BIOLOGY 
R 
G 


THE  MECHANICS  OF  THE 
DIGESTIVE  TRACT 


THE  MECHANICS  OF  THE 
DIGESTIVE  TRACT  < 


BY 


WALTER  C.  ALVAREZ,  M.D. 

Assistant  Professor  of  Research  Medicine 

George  Williams  Hooper  Foundation  for  Medical  Research, 

University  of  California  Medical  School 


WITH    TWENTY'TWO    ILLUSTRATIONS 


NEW  YORK 

PAUL  B.  HOEBER 

MGMXXII 


COPYRIGHT,  1922 
BY  PAUL  B.  HOEBER 

Published,  January,  1922 


Printed  in  the  United  States  of  America 


THESE  PAGES  ARE 
AFFECTIONATELY  DEDICATED 

TO 
MY  FATHER  AND  MOTHER 


46935 


PREFACE 

IN  1913,  while  doing  some  work  on  the  absorption  of 
gases  injected  into  loops  of  intestine,  I  noticed  differences 
in  irritability  in  different  parts  of  the  bowel;  that  is,  the 
jejunum  reacted  actively  to  distention,  while  the  ileum 
generally  responded  but  little.  It  promptly  occurred  to  me 
that  this  graded  difference  in  irritability  might  account 
for  the  downward  progress  of  food  in  the  bowel,  because  it 
seemed  reasonable  to  suppose  that  material  would  have  to 
move  from  the  more  irritable  and  active  regions  to  the  less 
irritable  and  active  ones.  While  attempting  to  show  these 
differences  in  irritability  with  excised  segments  of  intestine, 
I  found  that  the  rate  of  rhythmic  contraction  of  the  muscle 
is  graded  downwards  from  the  pylorus  to  the  ileocecal 
sphincter.  Remembering  how  much  the  heart  specialist  has 
profited  by  the  careful  study  of  conduction  along  a  similar 
rhythmic  gradient  from  the  sinus  node  to  the  ventricle,  I 
was  filled  with  the  hope  that  a  careful  analysis  of  the  gradi- 
ent found  in  the  bowel  might  throw  light  on  the  mechanism 
of  peristalsis  and  might  put  more  system  into  the  science 
of  gastro-enterology. 

As  time  goes  on  that  hope  seems  more  and  more  likely  to 
be  realized.  During  1915,  gradients  of  rhythmicity,  irrita- 
bility and  latent  period  were  found  in  the  stomach;  and  a 
sort  of  pacemaker  was  located  on  the  lesser  curvature  near 
the  cardia.  Later,  my  assistants  and  I  showed  that  in  addi- 
tion to  the  rhythmic  gradients  in  the  stomach  and  intestine, 
and  probably  underlying  them,  there  are  gradients  in  meta- 
bolism. Ways  were  found  in  which  these  chemical  gradients 
can  theoretically  be  upset;  and  actually  they  were  found 
upset  in  many  of  the  sickly  or  distempered  animals  studied. 


VIII 


PREFACE 


While  this  laboratory  work  was  going  forward,  a  careful 
review  was  made  of  our  knowledge  of  peristalsis  both  in 
health  and  disease;  and  it  was  found  that  the  idea  of  a 
gradient  of  forces  which  can  be  flattened  or  reversed  offers 
the  best,  the  simplest,  and  often  the  only  explanation  for 
many  of  the  phenomena  observed  by  the  physiologist,  the 
internist,  the  roentgenologist  and  the  surgeon. 

In  1920,  at  the  kind  invitation  of  Dr.  J.  T.  Case,  then 
President  of  the  American  Roentgen  Ray  Society,  I  pre- 
pared a  short  summary  of  my  views  which  was  presented 
before  the  Society's  meeting  in  Minneapolis  as  the  First 
Caldwell  Lecture.  This  little  book  has  developed  as  an 
elaboration  and  amplification  of  that  lecture.  I  only  hope 
it  will  be  a  help  and  convenience  to  those  practitioners  and 
roentgenologists  who  are  already  finding  the  gradient  theory 
useful  in  their  work,  and  who  wish  to  know  more  about  the 
subject.  I  have  tried  to  make  it  sufficiently  technical  for  the 
research  worker  in  physiology  and  yet  sufficiently  readable 
and  practical  for  the  medical  student  or  the  physician  who 
is  looking  for  help  on  a  clinical  or  surgical  problem.  Such 
students  and  practitioners  will  find  summed  up  in  Chapters 
IV,  VIII,  IX,  X  and  XI  most  of  the  data  essential  to  an 
understanding  of  the  mechanics  of  digestion;  and  with  the 
help  of  the  extensive  bibliography  and  the  paragraphs  at 
the  end  of  Chapter  XII,  they  can  easily  gain  access  to 
everything  else  of  value  which  has  been  written  on  the  sub- 
ject. I  think  the  chapter  on  technic  will  be  helpful  to  research 
workers,  because  the  information  embodied  in  it  has  hitherto 
been  scattered  through  many  articles  in  different  languages. 

Although  many  of  the  observations  upon  which  the  idea 
rests  have  been  verified  repeatedly,  and  although,  as  Wallace 
says,  "there  is  no  more  convincing  proof  of  the  truth  of  a 
comprehensive  theory  than  its  power  of  absorbing  and  find- 


PREFACE 


IX 


ing  a  place  for  new  facts,  and  its  capability  of  interpreting 
phenomena  which  had  been  previously  looked  upon  as 
unaccountable  anomalies,"  I  must,  in  all  fairness  to  my 
readers,  emphasize  the  fact  that  much  of  what  is  written  in 
Chapters  IX  and  X  is  purely  suggestive.  Thus  we  can  easily 
show  that  there  is  a  rhythmic  gradient  down  the  intestine; 
we  can  show  that  the  gradient  is  upset  in  a  distempered 
dog;  and  we  can  show  with  excised  segments  in  vitro  how 
easy  it  is  to  reverse  a  normal  gradient  by  adding  certain 
poisons  like  KCN  to  the  Locke's  solution.  We  can  speak 
positively  about  those  things,  but  we  must  be  careful  when 
we  come  to  say  that  the  reversal  found  in  the  sick  dog  is 
responsible  for  the  refusal  of  that  dog  to  eat,  and  for  the 
inability  of  his  stomach  to  pass  onward  the  food  which  has 
been  .forced  upon  him.  The  observations  are  highly  sugges- 
tive; the  theory  based  upon  them  is  proving  very  useful  in 
explaining  the  phenomena  of  indigestion,  but  we  must  not 
lose  sight  of  the  fact  that  it  is  a  theory;  that  it  has  weak 
places,  and  that  much  work  must  yet  be  done  upon  it. 

As  such  work  will  undoubtedly  modify  or  invalidate  some 
of  the  interpretations  which  seem  logical  at  this  time,  it 
would  certainly  have  been  safer  and  perhaps  better  if  I 
had  left  out  much  of  the  theorizing  which  now  enters  into 
this  little  book.  By  so  doing  I  could  undoubtedly  have  saved 
myself  from  future  regrets  and  criticism.  I  feel,  however, 
with  Darwin,  that  "without  speculation  there  is  no  good 
(or)  original  observation,"  and  that  "the  observer  can 
generalize  his  observations  incomparably  better  than  any 
one  else."  In  other  words,  it  would  seem  that  one  who  has 
wrestled  with  a  problem  day  and  night  for  many  years, 
and  who  has  collected  all  sorts  of  data  bearing  upon  it, 
should  be  most  fitted  to  theorize,  to  suggest,  and  to  point 
out  the  possible  applications  of  his  work.  He  can  furnish 


x  PREFACE 

the  greatest  number  of  jumping-off  places  for  further 
research;  and  even  those  who  are  incited  to  prove  him  wrong 
may  thereby  advance  the  field  of  knowledge.  The  only 
danger  is  that  he  and  some  of  his  less  critical  readers  may 
come  to  regard  the  suggestions  and  theories  not  as  a  scaffold- 
ing for  the  building  of  an  edifice  but  as  a  substantial  and 
finished  structure.  In  this  connection  a  writer  may  have  more 
to  fear  from  his  enthusiastic  friends  and  disciples  than  from 
his  enemies. 

Another  danger  at  this  time  is  that  some  of  the  building 
blocks  taken  from  other  edifices  to  be  used  now  as  foundation 
stones  may  not  bear  the  strain.  I  think  it  was  Darwin  who 
said  that  a  theory  builder  ought  really  to  write  to  many  of 
the  men  whom  he  quotes  to  see  whether  they  still  hold 
firmly  to  their  published  opinions,  and  whether  they  approve 
of  the  interpretations  which  he  is  placing  upon  their  work. 
It  is  even  better  when  he  can  repeat  many  of  the  more 
important  and  crucial  experiments  in  his  own  laboratory; 
and  more  of  that  I  hope  to  do  in  the  future.  For  the  present, 
I  can  only  say  that  few  statements  have  been  made  in  this 
book  which  are  not  based  either  upon  my  own  observations 
or  upon  a  careful  reading  of  several  original  articles. 

I  wish  gratefully  to  acknowledge  my  indebtedness  to 
Dr.  Walter  B.  Cannon  who  helped  me  to  get  started  on  these 
problems;  to  Dr.  Saxton  T.  Pope  who  aided  me  with  my 
first  little  laboratory  in  San  Francisco;  to  Dr.  George  H. 
Whipple,  Director  of  the  Hooper  Foundation,  whose  assist- 
ance and  wise  counsel  have  helped  me  over  many  a  diffi- 
culty; and  to  Miss  Esther  Starkweather,  Dr.  Fletcher  B. 
Taylor  and  Miss  Lucille  Mahoney,  who  have  assisted  me 
faithfully  with  many  of  the  experiments. 

WALTER  C.  ALVAREZ. 

SAN  FRANCISCO, 
Sept.  i,  1921. 


CONTENTS 

CHAPTER  PAGE 

I.  THE  AUTONOMY  OF  THE  DIGESTIVE  TRACT i 

Evolution  of  the  Nervous  System — Function  of  the 
Nerves  is  to  Expedite  Conduction — The  Autonomy 
of  the  Digestive  Tract. 

II.  THE  MYOGENIC  NATURE  OF  THE  RHYTHMIC  CONTRAC- 
TIONS AND  THE  FUNCTIONS  OF  AUERBACH'S  PLEXUS.       6 

III.  THE    SMOOTH    MUSCLE    OF    THE    GASTROINTESTINAL 

TRACT 16 

'  IV.  THE  DIFFERENT  TYPES  OF  PERISTALTIC  ACTIVITY.    .     21 
Esophagus — Stomach — Pylorus — Duodenal   Cap — 
Small  Bowel — Ileocecal  Sphincter — Colon. 

V.  GRADIENTS 32 

Conduction — Action  Currents — Gradient  in  the 
Heart — Gradients  in  Other  Organs — Gradient  in  the 
Intestine — Reversal  Experiments — A  Gradient  of 
Force. 

VI.  THE  UNDERLYING  BASIS  OF  THE  RHYTHMIC  GRADIENT.     43 
Anatomic  Gradient — Chemical  Gradient — Metabolic 
Gradients  in  the  Embryo — Bio-electric  Currents. 

VII.  OTHER  RELATED  GRADIENTS 52 

Latent  Period — Tone — Rhythmic  Tendency — Irrita- 
bility— Early  Observations  on  the  Rhythmic  Gradi- 
ent— Anatomic  Differences. 

VIII.  GRADED  DIFFERENCES  IN  THE  STOMACH  WALL  ...     69 
The  Primitive  Digestive  Tube  and  Its  Modifications 
—Differences  in  Rhythmicity — Differences  in  Tone — 
Differences  in  Irritability  and  Latent  Period — Differ- 
xi 


xii  CONTENTS 

CHAPTER  PAGE 

ences  in  Excised  Segments — Difference  in  Catalase 
Content — Clinical  Applications. 

IX.  PRACTICAL  APPLICATIONS  OF  THE  GRADIENT  IDEA.  .  76 
Factors  Altering  the  Gradients — (i)  Irritating 
Lesions — (2)  Ingestion  of  Food  with  Distension  of 
the  Bowel — (3)  Nervous  Stimuli— (4)  Toxic  De- 
pression— (5)  Drugs — Ways  in  Which  the  Various 
Factors  can  Alter  the  Gradient — Stimulation  at  the  • 
Upper  End  with  Possible  Steepening  of  the  Gradient 
—The  Mechanical  Control  of  the  Pylorus — Stimula- 
tion in  the  Middle — Stimulation  at  the  Lower  End- 
Constipation — Depression  at  the  Lower  End — An 
Illustrative  Simile — Dietary  Suggestions. 

X.  REVERSE  PERISTALSIS  AND  ITS  SYMPTOMS 114 

Reverse  Transport  often  Observed — (i)  Vomiting — 
(2)  Regurgitation — (3)  Heart-burn — (4)  Belching — 
(5)  Nausea — (6)  Coated  Tongue  and  Foul  Breath — 
(7)  Feeling  of  Fullness  after  Beginning  to  Eat — (8) 
Globus — (9)  Hiccup — (10)  "Biliousness." 

XL  OBJECTIONS  AND  DIFFICULTIES 134 

Vagotonia  and  Sympathicotonia — Extrinsic  Nerves 
of  the  Digestive  Tract — The  Involuntary  Nervous 
System — The  "Law  of  the  Intestine" — Keith's 
Theory. 

XII.  TECHNICAL  METHODS  AND  APPARATUS  .....:.    149 
The  Roentgen  Ray  and  the  Barium  Meal — Method 
of  Auer — Gastric  and  Duodenal  Tubes — Fistula? — 
Windows — Opening    under    Salt    Solution — Entero- 
.     graphs — Perfusion — Small  Excised  Segments. 

BIBLIOGRAPHY .    .    .    160 

INDEX  OF  AUTHORS 185 

INDEX  OF  SUBJECTS , 191 


THE  MECHANICS  OF  THE  DIGESTIVE 

TRACT 

CHAPTER  I 
THE  AUTONOMY  OF  THE  DIGESTIVE  TRACT 

THE  human  mind  is  not  ready  to  look  for  new  explana- 
tions for  well-known  phenomena,  or  even  to  accept 
them  when  found,  until  its  contentment  with  the 
old  explanations  has  been  disturbed.  Whenever  I  describe 
some  of 'the  regional  differences  in  behavior  which  can 
easily  be  demonstrated  in  the  excised  stomach  and  bowel, 
someone  is  almost  sure  to  say:  "Oh,  that  is  due  to  the  auto- 
nomic  and  the  sympathetic."  Another  says  it  is  a  "reflex." 
So  far  as  they  are  concerned  the  matter  is  settled,  and  why 
waste  more  time  on  it!  When  I  point  out  that  the  peculiarities 
persist  in  little  pieces  of  muscle  which  have  been  cut  out 
and  kept  in  the  ice  box  for  a  few  days,  these  individuals 
take  refuge  in  the  fact  that  there  are  ganglion  cells  in  Auer- 
bach's  plexus. 

Now,  the  most  paralyzing  thing  in  scientific  work  is  a 
facile  explanation  which  puts  a  stop  to  further  curiosity 
without  really  advancing  our  knowledge  of  the  subject; 
and  I  have  never  been  able  to  see  the  value  of  pushing  the 
explanation  for  a  mechanical  phenomenon  out  of  the  organ 
in  which  it  might  be  studied,  and  into  a  tiny  ganglion  where 
we  can  hardly  follow  it.  It  seems  to  me  that  many  even  of 
the  teachers  of  physiology  have  a  wrong  idea  of  the  nervous 
system  and  its  relation  to  the  viscera.  They  look  at  it  some- 


MECHANICS  OF  THE  DIGESTIVE  TRACT 


what  as  an  electrical  power  house  which  not  only  supplies 
the  motive  force  but  controls  the  activities,  let  us  say,  of 
the  various  trains  running  over  a  railroad.  My  analysis  of 
the  literature  makes  me  feel  that  we  should  look  at  it  more 
as  a  telephone  switchboard  with  wires  which  carry  messages 
of  warning  and  advice  from  one  engineer  to  another.  The 
trains  supply  their  own  power,  and  the  differences  in  speed 
and  other  activities  are  due  to  peculiarities  in  the  structure 
of  the  engines,  peculiarities  in  fuel,  differences  in  the  gradient 
of  the  road,  etc. 

EVOLUTION  OF  THE  NERVOUS  SYSTEM.  This  idea  comes 
out  more  clearly  as  we  study  the  development  of  the  nervous 
system  in  lower  forms  of  life.  First,  we  have  the  unicellular 
organisms  which  naturally  have  no  difficulty  with  conduc- 
tion and  do  not  have  nerves.  Next,  perhaps,  come  the 
sponges  with  muscles  but  still  no  nerves.  These  muscles 
respond  to  direct  mechanical  stimulation  transmitted  through 
the  overlying  epithelium.  There  is  a  little  conduction 
from  muscle  cell  to  muscle  cell,  but  it  is  so  slow  and  its  spread 
is  so  limited  that  there  is  no  coordination  between  the  move- 
ments of  adjacent  fingers  of  the  sponge  (Parker350).  Next 
in  the  scale  of  development  come  the  animals  with  nerve 
nets  interposed  between  the  epithelium  and  the  muscles. 
Such  a  nerve  net  in  the  sea  anemone  enables  the  animal, 
when  touched,  to  contract  all  over  at  one  time.  The  stimulus 
spreads  out  through  the  net  somewhat  as  ripples  spread 
from  a  stone  thrown  into  a  pond.  If  the  impulse  is  slight, 
only  a  few  muscles  will  respond  locally;  but  if  the  impulse  is 
strong,  every  muscle  in  the  animal  will  contract  (Bethe55). 
A  little  higher  in  the  scale  we  find  nerve  nets  which  are 
"polarized,"  that  is,  they  conduct  better  in  one  direction 
than  in  another  (Parker,350  p.  130).  We  shall  see  later  that 


AUTONOMY  OF  THE  DIGESTIVE  TRACT  3 

Auerbach's  plexus  is  probably  one  of  these  "polarized" 
nerve  nets.  The  trouble  with  this  type  of  nervous  system  is 
that  it  is  uncentralized.  There  is  no  single  organ  to  which 
experiences  can  be  referred  or  from  which  volitional  im- 
pulses can  em'anate.  Moreover,  a  stimulus  at  one  point  is 
likely  to  spread  all  over.  These  difficulties  are  overcome  in 
the  higher  animals  by  the  breaking  up  of  the  conducting 
paths  into  three  relays,  consisting  of  a  sensory,  a  connector 
and  a  motor  neurone.  The  connections  between  these  neu- 
rones are  so  made  that  impulses  can  pass  in  one  direction 
only.  Furthermore,  by  means  of  association  fibers,  impulses 
may  travel  to  smaller  or  larger  groups  of  muscles  where  they 
will  bring  about  coordinated  movements.  The  higher  the 
animal  is  in  the  scale  of  existence,  the  more  complicated 
and  more  numerous  become  these  association  fibers  with 
their  valve-like  synapses  (Parker348). 

THE  FUNCTION  OF  THE  'NERVES  is  TO  EXPEDITE  CON- 
DUCTION. It  must  not  be  forgotten,  however,  that  in  the 
more  complex  animals,  alongside  of  the  highest  type  of 
synaptic  system,  we  find  not  only  the  primitive  nerve  nets, 
as  in  the  intestine,  bladder  and  arteries,  but  we  find  evidence 
of  the  original  protoplasmic  transmission  from  cell  to  cell. 
Similarly,  in  a  modern  city  we  find,  alongside  of  the  tele- 
phone, the  original  messenger  boy.  The  thing  to  be  kept  in 
mind  is  that  the  nervous  system  in  all  its  stages  of  develop- 
ment has  one  big  function,  and  that  is  to  expedite  conduction. 
Loeb270  has  shown  by  numberless  experiments  that  there  is 
no  storage  of  wisdom  in  ganglia  and  "centers."  He  takes 
up  one  complicated  reflex  after  another;  he  takes  up  "purpose- 
ful reactions"  and  "instincts,"  and  shows  that  they  are  due 
simply  to  localized  peculiarities  of  structure  and  chemical 
affinity. 


4      THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

All  sorts  of  properties  have  been  ascribed  to  the  ganglion 
cells,  but  it  appears  now  that  these  structures  serve  more 
as  nutritional  centers  for  the  nerve  fibers  than  as  storehouses 
of  wisdom  and  tone.  Bethe54  (p.  403)  was  able  by  micro- 
dissection  to  trim  off  all  such  cells  from  the  nerve  bundle 
going  to  one  of  the  antennae  of  a  small  crayfish,  and  found 
no  difference  in  the  tone  and  reflex  irritability  of  the  muscles 
in  that  antenna.  This  suggests  strongly  that  the  reflex  im- 
pulses do  not  even  have  to  pass  through  the  ganglia,  let 
alone  originate  in  them.  Similarly,  if  we  remove  the  central 
ganglion  from  an  ascidian,  its  complicated  reflexes  are  still 
carried  out.  The  only  difference  is  that  they  need  a  stronger 
stimulus  and  they  are  executed  more  slowly  because  conduc- 
tion is  then  effected  through  the  nerve  net  (Loeb,270  p.  35, 
Jordan221).  Most  of  us  think  of  the  pupillary  response  to 
light  purely  as  a  complicated  cerebral  reflex,  but  it  has  been 
shown  that  not  only  does  the  pupil  of  the  excised  eye  react, 
but  small  muscle  bundles  cut  out  from  the  iris  will  respond 
directly  to  the  stimulus  of  a  strong  light  (Parker,350  p.  51). 
Even  more  remarkable  is  the  fact  that  a  beheaded  shark  can 
swim  as  if  there  were  little  the  matter  with  him,  and  a  frog 
can  catch  flies,  swallow  and  digest  them  for  weeks  after  his 
forebrain  has  been  removed. 

Many  other  examples  might  be  given  of  the  simplicity  of 
the  mechanisms  which  bring  about  complicated  and  purpose- 
ful reactions  in  small  excised  segments  of  animals,  but  we 
must  hurry  on  to  an  analysis  of  the  problems  in  the  particular 
field  under  discussion — the  intestine. 

THE  AUTONOMY  OF  THE  DIGESTIVE  TRACT.  We  find,  as 
might  have  been  expected,  that  after  the  preliminary  shock 
wears  off  digestion  goes  on  quite  well  after  section  of  the 
vagi  and  the  splanchnics  (Cannon,81  Rubaschow,379  Krehl241). 


AUTONOMY  OF  THE  DIGESTIVE  TRACT  5 

That  observation  has  been  made  by  so  many  physiologists 
that  there  can  be  no  question  about  it.  Furthermore,  peris- 
talsis and  strong  rhythmic  contractions  can  be  obtained  in 
the  excised  stomach  and  intestine,  either  perfused  or  placed 
in  oxygenated  Locke's  solution;  in  short  segments  of  bowel, 
and  even  in  bits  of  muscle  removed  from  the  wall.  It  is 
clear,  then,  that  the  gastro-intestinal  tract  is  largely  auto- 
nomous; that  is,  it  carries  within  itself  the  mechanisms 
essential  to  peristalsis.  This  point  cannot  be  emphasized 
too  strongly,  because  it  seems  to  me  that  the  failure  to  grasp 
it  is  the  greatest  stumbling  block  to  further  advance  in  our 
understanding  of  the  subject.  It  is  undoubtedly  true  that 
the  extrinsic  nerves  have  much  to  do  with  peristalsis  both 
in  health  and  disease,  but  it  is  very  helpful  in  simplifying 
our  problems  to  recognize  that  the  tract  can  get  along  with- 
out any  outside  help  or  interference.  This  should  make  us 
the  more  willing  and  eager  to  study  the  all-important  local 
mechanisms. 


CHAPTER  II 

THE  MYOGENIC  NATURE  OF  THE  RHYTHMIC 

CONTRACTIONS   AND  THE  FUNCTIONS  OF 

AUERBACH'S  PLEXUS 

HAVING  established  clearly  that  the  digestive  tract  is 
highly  autonomous,  and  that  the  mechanism  produc- 
ing peristalsis  is  to  be  found  in  the  wall  of  the  gut, 
the  next  question  is:  Which  of  the  two  structures  in  that 
wall  is  the  more  important-^the  muscle  or  the  nerve  net? 
On  turning  to  the  various  textbooks  on  physiology  we  find 
the  definite  statement  made  that  the  rhythmic  contractions 
of  the  bowel  are  neurogenic,  and  due  to  stimuli  coming 
from  the  ganglion  cells  in  Auerbach's  plexus.  The  writers 
all  base  this  opinion  on  the  second  and  fourth  papers 
by  Magnus290  and292  who  found  that  when  he  stripped  the 
longitudinal  muscle  from  the  circular,  the  plexus  always 
came  away  with  the  former  because  it  lies  protected  there 
in  little  grooves.  His  microphotographs  of  the  adjoining 
surfaces  of  the  two  muscle  coats  show  on  one  side  the  plexus 
practically  intact  and  on  the  other  only  a  few  isolated  frag- 
ments. As  he  says,  "AuJ  der  Jreigelegten  Oberfldche  der 
Ringmuskulatur  der  Auerbachsche  Plexus  entweder  garnicht 
vorhanden  ist,  oder  nur  ganz  geringe  Bruchstiicke  oder  ganz 
vereinzelte  Knotenpunkte  davon  nachweisen  /assen"290  (p.  357). 
The  thing  which  impressed  him  was  that  the  longitudinal 
muscle,  with  the  nerves,  contracted  rhythmically,  while  the 
circular  did  not.  Moreover,  the  circular  muscle  differed 
from  the  longitudinal  in  that  it  could  be  tetanized  and  that 

6 


THE  RHYTHMIC  CONTRACTION  7 

it  had  a  refractory  period.291  These  differences  were  so 
striking  that  Magnus  felt  no  doubt  about  the  neurogenic 
origin  of  the  rhythmic  contractions;  and  his  positive  state- 
ments have  been  quoted  unhesitatingly  ever  since.  Un- 
fortunately, few  physiologists  seem  to  have  noticed  that 
in  Magnus*  later  work  he  ran  into  serious  perplexities.  We 
find  in  his  fifth  paper293  the  admission  that  when  he  added  a 
little  pilocarpin,  strophanthin  or  barium  to  the  Locke's 
solution  he  got  good  rhythmic  contractions  not  only  in  the 
longitudinal  strips  but  also  in  the  carefully  denervated  and 
previously  quiescent  circular  ones  (Fig.  lA).  At  first  he 
thought  that  this  was  due  to  some  effect  of  the  drugs  on 
remnants  of  the  plexus  left  on  the  outer  surface  of  the  muscle, 
so  he  seared  that  surface  with  crystals  of  silver  nitrate. 
This  treatment  put  an  end  to  the  rhythmic  contractions 
even  in  the  presence  of  pilocarpin,  strophanthin  and  barium, 
but  segments  which  reacted  in  a  typically  denervated  way 
with  these  drugs  still  contracted  rhythmically  under  the 
influence  of  physostigmin.  He  remained  satisfied  that  these 
segments  were  thoroughly  freed  from  the  plexus  but  still 
seemed  to  feel  that  the  fact  that  the  rhythmic  contractions 
were  brought  out  by  a  drug  made  them  a  little  different 
from  the  normal  ones.  He  was  not  so  surprised  at  the  action 
of  physostigmin  because  he  had  observed  previously  in  a 
marine  worm  that  when  the  nervous  system  was  completely 
removed  (easily  done  on  account  of  the  large  size  of  the 
fibers)  the  muscles  would  contract  rhythmically  in  weak 
solutions  of  that  drug. 

Certainly,  it  is  remarkable  that  when  a  worker  publishes 
negative  results,  and  later  positive  ones,  the  negative  results 
should  become  one  of  the  corner  stones  of  physiology,  upon 
which  opinion  remains  unanimous. 

It  is  the  more  remarkable  when  we  note  the  large  amount 


8       THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 


Seit  16  Minuten 
ft  eg  I'liysostigmin 


0.2  me  Strophautliin  Thorns      A 


FIG.  i. 
(A)  Plexus-free  preparation  contracting  rhythmically.  (From  Magnus.) 

(B)  Denervated  muscle.  (From  Gunn  and  Underbill.} 
(C)  Tracing  from  one  of  my  own  experiments  with  denervated  muscle. 
(D)  Rhythmic  changes  in  the  evolution  of  hydrogen  when  acids  act  on 
chromium.  Note   increase   of  rate  with  rise  in  temperature  of  the  solution. 
(From  Ostwald.) 


THE  RHYTHMIC  CONTRACTION  9 

of  evidence  from  other  workers,  showing  that  muscle  alone 
has  a  strong  tendency  to  rhythmic  contraction.  It  is  remark- 
able again  that  no  one  seems  to  have  paid  any  attention  to 
the  excellent  paper  by  Gunn  and  Underhill,174  who  repeated 
Magnus'  work  with  great  care.  They  cut  down  the  shock 
by  making  the  dissection  in  iced  Locke's  solution,  which 
acted  as  an  anesthetic.  Instead  of  searing  the  outer  surface 
of  the  muscle  to  remove  all  vestiges  of  the  plexus  they 
stripped  off  only  a  few  fibers  from  the  mucous  membrane 
side  and  used  those  for  their  experiments.  In  this  way  they 
obtained  muscle  which  certainly  must  have  been  plexus- 
free  and  which  contracted  rhythmically,  as  can  be  seen  in 
Fig.  iB,  copied  from  their  article. 

Remembering  that  the  intestinal  muscle  from  the  dog 
often  contracts  better  after  from  one  to  three  days  in  the 
ice-box,  Miss  Mahoney  and  I  repeated  Gunn  and  Underhill's 
work,  using  segments  of  duodenum  twenty-four  hours  old; 
and  even  without  the  precaution  of  keeping  the  tissue. cold, 
we  found  little  difficulty  in  getting  rhythmic  contractions 
from  strips  of  circular  muscle.  Although  Magnus  says  he 
waited  hours,  it  may  be  that  his  failures  could  have  been 
avoided  by  waiting  longer.  We  find  that  some  strips  will 
start  beating  only  after  they  have  been  for  six  or  seven  hours 
in  the  solution.  This  period  of  waiting  can  be  shortened 
greatly  by  adding  a  trace  of  barium  to  the  solution.  The 
effect  of  this  drug  is  generally  the  same  on  the  longitudinal 
as  on  the  circular  strips.  After  obtaining  these  records,  the 
strips  were  examined  histologically,  and  in  some  of  them  it 
could  be  proved  that  only  the  inner  half  of  the  circular 
layer  had  been  used. 

I  feel,  therefore,  that  we  must  admit  that  the  smooth 
muscle  of  the  intestinal  wall  shares  in  that  tendency  to 
rhythmic  contraction  which  is  seen  so  universally  in  muscular 


io     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

tissue.  This  is  what  we  should  expect  when  we  remember 
that  strips  of  intestine  beat  even  better  on  the  second  or  third 
day  than  on  the  first.  I  have  records  showing  that  the  rate 
is  even  faster  and  the  rhythm  more  regular  on  the  second 
day  (Alvarez10).  When  we  remember  that  some  sympathetic 
ganglia  fail  to  function  within  a  few  minutes  after  the 
circulation  ceases,  it  is  hard  to  believe  that  in  the  bowel  their 
functions  can  actually  improve  after  death.  It  is  much  easier 
to  believe  that  the  improved  contractility  is  due  to  the 
removal  of  nervous  inhibitions,  and  to  the  wearing  off  of  the 
shock  of  cutting.  Moreover,  Bayliss  and  Starling39  (p.  138) 
found  that  cocain  applied  to  the  surface  of  the  bowel  abol- 
ished the  myenteric  reflex  and  with  it  the  power  of  the 
bowel  to  pass  on  a  bolus.  It  improved,  however,  the  ampli- 
tude and  regularity  of  the  rhythmic  contractions.  As  nicotin 
had  exactly  the  same  effect  when  injected  repeatedly  and  in 
large  doses,  they  had  good  reason  to  infer  that  they  had 
paralyzed  the  plexus;  that  the  myenteric  reflex  is  due  to  the 
nerves,  and  that  the  rhythmic  contractions  are  due  to  the 
muscle.  Although  I  am  rather  prejudiced  against  physiologic 
conclusions  based  on  the  assumed  selective  action  of  poisons, 
it  does  seem  to  me  that  we  must  face  this  evidence  squarely. 
Certainly,  we  cannot  go  on  quoting  these  experiments  to 
show  that  the  progress  of  food  through  the  bowel  is  based  on 
a  nervous  mechanism,  and  Magnus*  experiments  to  show 
that  the  rhythmic  contractions  are  also  based  upon  it.  If 
Bayliss  and  Starling  were  right  Magnus  was  wrong,  and 
vice  versa. 

When  one  remembers  how  common  rhythmical  processes 
are  in  nature  it  is  hard  to  understand  why  physiologists 
tend  so  often  to  ascribe  those  observed  in  muscle  to  that 
highly  specialized  organ,  the  nervous  system.  Curves 
closely  resembling  those  traced  by  a  frog's  heart  can  be 


THE  RHYTHMIC  CONTRACTION  .  u 

produced  by  a  simple  physico  chemical  reaction  (Fig.  iD). 
These  tracings  from  Ostwald's347  article  were  produced 
by  attaching  an  ordinary  tambour  to  a  flask  in  which 
hydrochloric  acid  was  acting  on  chromium  with  the  evolu- 
tion of  hydrogen.  Rhythmic  changes  take  place  in  the 
metal  which  make  it  alternately  resistant  and  subject 
to  attack  by  the  acid.  Similar  rhythmic  changes  occur  in 
the  rate  of  catalytic  decomposition  of  hydrogen  peroxide 
in  contact  with  mercury,  owing  to  the  alternate  formation 
and  dissolution  of  a  surface-film  of  "peroxidate."  In  both 
of  these  reactions  electricity  plays  a  large  part,  much  as 
it  does  in  the  animal  body.  When  water  drips  at  regular 
intervals  from  a  reservoir  we  have  a  rhythmic  response 
to  a  constant  force.  Forbes  and  Gregg154  have  remarked 
upon  several  instances  of  this  type  of  reaction  in  the  body. 
Quincke  produced  rhythmic  alterations  in  the  shapes  of 
air  bubbles  trapped  under  water  and  placed  in  the  path 
of  a  fine  stream  of  alcohol  (Loeb,270  p.  22).  The  pulsations 
of  the  bubble  closely  resemble  those  of  a  heart,  and  are  due 
to  alterations  in  the  surface  tension.  Turning  from  these 
purely  chemical  and  physical  phenomena  we  learn  that 
Bose66  has  observed  beautifully  rhythmic  contractions  in 
the  leaflets  of  certain  plants.  A  little  higher  in  the  scale, 
we  -find  animal  tissues,  not  yet  muscular  in  structure,  but 
possessing  the  power  of  rhythmic  contraction.  I  need  only 
mention  cilia  and  the  tails  of  spermatozoa. 

The  heart  beat  seems  to  originate  in  muscle  or  muscle- 
like  tissue  except  in  the  Limulus,  a  very  primitive  type 
of  crab;  and  even  in  that  animal,  Carrey157  has  shown  that 
the  denervated  muscle  will  contract  rhythmically  if  put 
into  N/2  NaCI.  The  heart  of  the  embryo  chick  beats  after 
twenty-nine  hours  of  incubation,  although  nerve  cells  do 
not  reach  it  until  the  sixth  day  (Parker,350  p.  55,  Verzar439); 


12    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

and  even  the  isolated  heart  muscle  cells  in  tissue  cultures 
have  been  observed  to  beat  (Burrows78).  The  same  thing 
was  seen  by  Lewis  and  Lewis  in  cultures  of  smooth  muscle.264 
The  retractor  penis  of  the  dog  is  made  up  of  smooth  muscle; 
it  has  no  ganglia  (Fletcher,151  Fisher150)  and  yet  it  contracts 
rhythmically  when  excised  (De  Zilwa,454  Edmunds133). 
Loeb  has  shown,  moreover,  that  even  striated  muscle  will 
contract  rhythmically  in  the  proper  concentration  of  NaCI 
(Loeb>271  p.  78,  Mines321).  Hydromedusa  stops  pulsating 
when  the  nerve  net  is  excised,  and  this  was  supposed  to 
prove  the  nervous  origin  of  the  beat  until  Loeb,270  p.  18) 
showed  that  the  muscle  will  start  up  again  if  the  concentra- 
tion of  the  sea  water  is  changed.  Romanes  found,  moreover, 
that  the  nerveless  center  of  another  type  of  jellyfish, 
Acalepha,  will  beat  in  sea  water. 

It  is  clear,  then,  that  although  some  forms  of  muscle 
do  not  beat  rhythmically  by  themselves  when  immersed 
in  their  body  fluids  or  in  Locke's  solution,  they  will  beat 
when  placed  in  a  suitable  medium.  As  the  denervated 
intestinal  muscle  will  beat  in  Locke's  solution,  I  see  no 
reason  for  saying  that  it  is  normally  dependent  upon 
Auerbach's  plexus  for  its  rhythmic  stimuli.  About  the  only 
evidence  that  I  know  of  now  in  favor  of  the  neurogenic 
origin  is  that  presented  by  Yanase,453  who  observed  per- 
istalsis in  embryo  guinea  pigs  only  after  the  twenty-sixth 
day,  when  the  myenteric  plexus  and  the  longitudinal  muscle 
appear.  This  negative  evidence  is  not  conclusive  for  a  number 
of  reasons. 

Although  the  muscle  can  contract  rhythmically  by  itself 
it  is  normally  in  close  relationship  to  its  nerves.  As  Gaskell160 
(p.  105)  says,  these  nerves  are  there  for  a  purpose  and  the 
muscle  contracts  better  for  their  presence.  In  actual  life 
it  makes  little  difference  which  one  has  the  more  to  do  with 


THE  RHYTHMIC  CONTRACTION  13 

the  rhythmicity  because  they  both  work  together;  and  the 
only  reason  I  have  devoted  so  much  space  to  the  matter 
is  that  the  acceptance  of  the  neurogenic  explanation  for 
the  activities  of  the  bowel  causes  the  student  to  lose  sight 
of  the  great  need  for  studying  the  regional  peculiarities 
of  the  muscle. 

THE  FUNCTION  OF  AUERBACH'S  PLEXUS.  The  next  ques- 
tion is,  if  the  muscle  can  contract  by  itself,  what  is 
Auerbach's  plexus  good  for?  It  almost  undoubtedly  serves 
for  the  conduction  of  stimuli  and  the  coordination  of  move- 
ments. A  centipede  is  a  colony  of  legs  each  segment  of  which 
can  walk  and  attend  to  its  own  affairs.  Normally  they  all 
follow  the  lead  of  the  head  segment.  If  we  cut  the  nerve  cord 
we  get,  in  effect,  two  independent  centipedes,  one  of  which 
may  want  to  stand  still  while  the  other  wants  to  walk  off; 
The  result  is  that  the  animal  turns  from  time  to  time  to 
bite  savagely  at  its  rear  half  which  it  seems  to  regard  only  as 
a  foreign  body  (Carlson,94  p.  286).  The  hind  end  of  a  plana- 
rian  worm  which  has  grown  too  long  for  efficient  conduction 
fails  to  follow  the  lead  of  the  front  end.  It  takes  firm  hold 
of  the  aquarium  wall;  the  front  end  crawls  on  unconcernedly, 
and  the  worm  is  pulled  in  two  (Child,111  p.  131).  We  would 
probably  have  similar  conflicts  in  the  bowel,  with  colic  and 
dynamic  ileus  as  a  result,  if  rapid  conduction  were  not 
possible  through  the  myenteric  plexus  and  through  the 
nerves  in  the  mesentery.  My  own  measurements  indicate 
that  impulses  travel  about  20  cm.  per  second  through  the 
plexus  (Alvarez  and  Starkweather18).  This  seems  pretty 
slow  for  nervous  transmission,  but  it  must  be  remembered 
that  these  nets  represent  early  stages  in  the  evolution  of 
conducting  tissue,  and  the  rate  in  the  bowel  is  very  similar 
to  that  observed  in  the  nets  of  some  of  the  lower  organisms 


i4    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

(Lillie,266  p.  417;  Jenkins  and  Carlson,215  Hecht,181  Parker,349 
p.  231).  The  rush  waves  in  the  bowel  which  travel  from 
muscle  fiber  to  muscle  fiber  cover  about  4  cm.  per  second 
in  the  rabbit.  Impulses  through  the  mesenteric  nerves 
seem  to  travel  about  200  cm.  per  second.  The  existence 
of  such  extra-mural  means  of  transmission  has  been  proved 
by  obtaining  responses  to  stimulation  on  the  farther  side  of 
gaps  in  which  the  bowel  has  been  removed  (Mayer,304  p.  451; 
Kirschner  and  Mangold,236  p.  491 ;  Roith,375  Marbaix,300  p.  283; 
Surmont  and  Dubus417). 

Another  function  of  Auerbach's  plexus  is  probably  to 
make  the  muscles  respond  properly  to  stimuli  coming  from 
the  under-lying  mucous  membrane.  These  stimuli  are  collect- 
ed by  Meissner's  plexus  and  transmitted  to  Auerbach's  by 
connecting  fibers.  Cannon86  (p.  184)  and  Jacobj213  have 
remarked  that  the  peristaltic  movement  seem  to  be  modified 
continually  by  the  chemical  nature  of  the  intestinal  contents ; 
and  we  know  that  inflammation  of  the  mucous  membrane 
and  its  irritation  by  certain  purges  will  give  rise  to  height- 
ened peristalsis  (Katsch  and  Borchers,228  p.  237).  On  the 
other  hand,  pricks  from  sharp  foreign  bodies  like  pins  within 
the  gut  are  said  to  inhibit  the  overlying  muscle  so  that 
perforation  will  be  avoided  (Exner,145  A.  Miiller333). 

Still  another  function  of  the  plexus  is  probably  to  keep 
the  muscle  from  being  too  active  (Bayliss  and  Starling,41 
p.  133)  or  from  contracting  down  into  a  hard  knot.  It  is 
well  known  to  experimental  zoologists  that  when  smooth 
muscle  is  cut  off  from  its  nervous  connections  its  tone  is 
likely  to  rise  to  a  point  where  rhythmic  contractions  are  no 
more  possible  (Magnus,289  Jordan,220  p.  210,  Biedermann58). 
Magnus*  difficulty  in  getting  good  records  from  the  dener- 
vated  circular  muscle  was  due  probably  in  part  to  the  spas- 
modic contraction  which  appeared  when  he  removed  the 


THE  RHYTHMIC  CONTRACTION        15 

plexus.  Similarly,  Cannon81  (p.  432)  observed  a  remarkable 
shrinkage  of  the  stomach  into  a  hard  narrow  tube  when  he 
cut  the  extrinsic  nerves.  The  condition  corresponds  some- 
what to  that  seen  in  the  spastic  paralyses  of  the  voluntary 
muscles  in  man  after  cerebral  hemorrhages.  It  may  easily 
be  that  some  of  the  contraction  rings  seen  in  spasmodic 
ileus,  in  infantile  pyloric  stenosis,  and  in  Hirschsprung's 
disease  are  due,  not  to  an  excess  of  nervous  stimulation 
but  to  an  absence  of  it. 

Many  have  assumed  that  Auerbach's  plexus  serves  to 
bring  about  reflexes  in  the  intestinal  wall,  but  this  seems 
unlikely  because  neither  the  anatomists  nor  the  physiologists 
have  been  able  to  demonstrate  the  requisite  nervous  arcs. 
A  recent  attempt  to  show  them  with  the  help  of  strychnin 
also  failed.  That  drug  was  chosen  because  it  seems  to  act 
mainly  on  the  synapses  between  neurones:  it  closes  the  gaps, 
lowers  the  threshold  and  exaggerates  reflexes  (Porter363). 
Moore  has  pointed  out  that  we  can  probably  judge  of  the 
part  played  by  synapses  in  any  particular  organism's  nervous 
system  by  the  extent  to  which  it  responds  to  strychnin 
(Moore;325  Knowlton  and  Moore;238  McGuigan  and 
Becht;314  McGuigan,  Keeton  and  Sloan;315  Sherrington,397 
pp.  42  and  in).  The  simpler  animals  with  pure  nerve  nets 
hardly  respond  at  all.  It  is  very  suggestive,  then,  that  Miss 
Starkweather  and  I  could  find  no  difference  in  the  reactions 
of  either  the  intact  or  excised  bowel  before  and  after  giving 
lethal  doses  of  strychnin  (Alvarez  and  Starkweather18). 
Apparently  the  myenteric  plexus  is  a  fairly  simple  nerve 
net  without  synapses,  "centers"  or  reflex  arcs.  As  I  said  be- 
fore, its  principle  function,  like  that  of  the  nerves  elsewhere, 
is  to  expedite  conduction. 


CHAPTER  III 

THE  SMOOTH  MUSCLE  OF  THE  GASTRO- 
INTESTINAL TRACT 

I  HAD  not  been  working  long  on  the  problems  of  peristalsis 
before  I  became  impressed  with  the  need  for  learning 
everything  possible  about  smooth  muscle.  More  and  more 
it  seemed  to  me  that  if  I  knew  just  what  that  tissue  would  do 
under  certain  conditions  I  could  explain  many  of  the  activi- 
ties of  the  gut.  I  felt  still  surer  of  that  when  I  found  how 
autonomous  the  muscle  is,  and  how  strong  its  tendency  is  to 
contract  rhythmically,  even  in  the  absence  of  nervous 
stimuli.  It  would  seem  well,  then,  in  this  chapter  to  enumer- 
ate briefly  some  of  the  properties  and  pecularities  of  smooth 
muscle.  Although  from  now  on  the  term  muscle  will  often  be 
used,  it  must  not  be  forgotten  that  there  are  nerve  cells 
scattered  amongst  the  contractile  fibers,  connecting  them 
together  and  modifying  their  reactions.  To  be  exact,  we 
should  probably  use  the  term  musculoneural  apparatus 
except  in  those  instances  in  which  we  refer  to  denervated 
muscle,  but  the  word  is  long  and  unwieldy,  and  after  this 
explanation,  I  think  it  will  be  safe  to  use  the  shorter  term 
muscle. 

As  is  well  known,  smooth  muscle  is  made  up  of  spindle- 
shaped  cells  which  vary  in  size,  shape,  number  of  nuclei, 
etc.,  in  different  animals  and  in  different  parts  of  the  same 
animal  (Ranvier,369  p.  433,  Pompilian,362  Lapique,253 
McGill,313  Schultz,390  Bottazzi  and  Grtinbaum,70  Paukul,353 
Schiefferdecker385).  As  a  rule  it  contracts  more  sluggishly 

16 


MUSCLE  OF  THE  GASTRO- INTESTINAL  TRACT    17 

than  striated  muscle  does;  it  takes  longer  to  get  started,  and 
it  is  slower  in  recovering  its  original  length.  Incidentally, 
the  greatest  difficulty  in  working  with  this  type  of  muscle 
arises  from  the  fact  that  one  can  never  be  sure  what  its 
original  length  was  because  of  the  constant  tone  changes. 
After  a  number  of  strong  stimuli  or  sometimes  after  only 
one,  the  muscle  may  become  quite  refractory  (Parker,350 
p.  1 68,  Jennings,216  Wood  worth,451  p.  39),  but  after  a  long 
rest  it  seems  to  get  on  a  hair  trigger  again  so  that  it  responds 
powerfully  and  explosively  to  a  slight  stimulus.  That  is  the 
condition  of  the  digestive  tract  after  the  night's  rest;  and  it 
probably  has  much  to  do  with  the  fact  that  most  of  us  have 
the  daily  bowel  movement  in  the  morning,  immediately 
after  breakfast.  With  an  animal  open  under  salt  solution,  one 
can  often  start  a  rush  wave  down  the  bowel  by  pinching  the 
duodenum.  For  some  time  afterwards,  similar  pinches  will 
have  no  effect,  but  if  we  wait  long  enough  we  will  again  find 
the  bowel  so  sensitive  that  the  slightest  stimulus  will  start 
a  wave. 

Another  characteristic  of  smooth  muscle  is  its  ability 
to  maintain  a  firm  and  lasting  contra tion  without  fatigue. 
We  see  this  in  the  muscles  which  close  the  shells  of  bivalves, 
and  we  see  it  in  the  wall  of  the  colon.  It  is  interesting 
that  the  muscle  in  a  bivalve  consists  of  two  parts:  one 
which  closes  the  shell  and  the  other  which  locks  it  closed. 
By  cutting  first  one  and  then  the  other  it  can  be  shown 
that  neither  one  can  do  the  work  of  the  other  (Parnas351). 
Similarly,  if  a  man  of  average  strength  tries  to  hold  his 
arm  out  perpendicularly  to  his  body  he  soon  finds  it  a 
most  painful  and  fatiguing  experiment.  The  deltoid  was 
not  designed  for  such  heavy  work,  but  the  glutei  and  back 
muscles  are  carrying  much  heavier  loads  all  day  and  they 
do  not  complain  (Sherrington,398  p.  191).  We  learn  from  this 


i8     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

that  there  are  all  kinds  of  muscles,  all  suited  to  different 
purposes.  Some,  like  those  in  the  wings  of  insects,  must 
contract  300  times  a  second;  others  like  those  in  the  wings 
of  a  hen  have  little  to  do.  Those  who  think  all  muscle  is  the 
same  forget  the  differences  between  the  white  and  dark 
meats  of  chicken,  between  the  heart  and  the  gizzard;  between 
tenderloin,  roundsteak  and  tongue.  I  have  gone  into  these 
differences  so  at  length  because  I  believe  there  are  similar 
differences  between  the  muscle  in  the  cardiac  and  pyloric  ends 
of  the  stomach  (Alvarez5;6?7?8);  between  that  in  the  small 
intestine  and  that  in  the  cecum  (Alvarez  and  Starkweather13) 
and  colon  (Alvarez10).  The  muscle  on  the  lesser  curvature 
near  the  cardia  is  soft  to  the  touch  like  coagulated  fibrin;  that 
in  the  pyloric  antrum  is  tough  like  gizzard  and  has  a  different 
color.  If  we  stimulate  the  two  with  an  electric  current  or  with 
a  pinch,  we  get  two  entirely  different  contraction  curves;  and 
if  we  put  them  into  warm  oxygenated  Locke's  solution  we  get 
two  different  types  of  rhythmic  activity.  These  differences 
should  be  expected  when  we  remember  that  the  upper  and 
lower  ends  of  the  stomach  have  different  kinds  of  work  to  do. 
The  upper  end  serves  largely  as  a  hopper  to  hold  the  food; 
the  lower  as  the  mill  to  do  the  heavy  work.  More  of  these 
local  peculiarities  will  be  described  later. 

Another  characteristic  of  smooth  muscle  in  hollow  organs 
is  its  responsiveness  to  tension.  Most  of  the  motor  activities 
of  the  stomach  and  bowel  are  brought  about  and  regulated 
largely  by  the  internal  pressure  due  to  the  presence  of  food 
or  gas.  Cannon86  (p.  187)  has  shown  that  the  rhythmic 
segmentation  in  the  small  intestine  is  due  simply  to  the  fact 
that  those  muscle  fibers  which  are  stretched  tend  to  contract. 
Their  contraction  increases  the  pressure  in  neighboring 
segments,  and  so  the  process  goes  on.  Cannon  has  shown 
also  that  the  waves  in  the  stomach  tend  to  appear  at  those 


MUSCLE  OF  THE  GASTRO- INTESTINAL  TRACT     19 

places  where  the  internal  pressure  balances  the  local  tone 
of  the  muscle.  If  the  pressure  is  too  little  or  too  great  there 
may  be  no  waves  (Cannon,86  p.  189,  Straub,414  Wislocki  and 
O'Connor449).  We  know  also  that  when  a  man  has  been 
purged,  his  bowels  are  not  likely  to  move  for  a  few  days. 
This  has  been  supposed  to  be  due  to  an  astringent  or  con- 
stipating action  of  the  purge,  but  I  have  considerable  evi- 
dence to  show  that  it  is  due  simply  to  the  lack  of  tension  in 
the  colon.  The  bowel  has  to  fill  up  to  a  certain  point  before 
the  muscle  fibers  will  be  stretched  enough  so  that  they  will 
contract  well.  As  Cannon  points  out,  these  reactions  to 
stretching  are  purely  local  and  are  not  brought  about  by 
nervous  reflexes. 

Smooth  muscle  shortens  also  under  the  influence  of  direct 
irritation.  Thus  we  find  spasmodic  contraction  of  the  cardia, 
pylorus,  ileocecal  sphincter  and  anus  when  there  is  ulceration 
or  inflammation  near  by.  We  find  hourglass  contractions  of 
the  stomach  opposite  ulcers  on  the  lesser  curvature;  and 
shrunken  and  irritable  caps  with  ulcers  in  that  region. 
From  a  diagnostic  standpoint  it  is  unfortunate  that  carcino- 
matous  tissue  often  fails  to  stimulate  the  muscle  in  this  way. 
Particularly  in  the  colon,  where  the  muscle  is  most  sluggish, 
carcinomas  will  often  remain  symptomless  until  they  block 
the  lumen  mechanically.  Some  of  the  sphincter  spasms  that 
are  seen  with  inflammations  or  ulcers  in  various  parts  of  the 
digestive  tract  may  be  due  simply  to  a  greater  irritability 
of  the  sphincters  as  compared  with  the  rest  of  the  gut. 
With  a  lower  threshold  they  would  be  very  likely  to  pick  up, 
and  respond  to  stimuli  which  are  ineffective  for  adjacent 
muscle  fibers.  As  I  shall  point  out  later  in  Chapter  VIII,  the 
muscle  fibers  in  the  pyloric  sphincter  actually  are  more 
irritable  than  the  fibers  in  the  rest  of  the  antrum  (Alvarez,6 
p.  326). 


20     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

Those  who  would  like  to  go  more  fully  into  the  physiology 
of  smooth  muscle  can  get  an  entree  into  the  subject  by 
reading  the  encyclopedic  articles  of  Griitzner171  and 
Schultz390>391). 

The  following  chapter  deals  with  the  peculiarities  in  peri- 
stalsis found  in  different  parts  of  the  digestive  tract,  peculiar- 
ities which  are  shown  to  be  due  largely  to  local  differences  in 
the  structure  and  physiological  properties  of  the  musculo- 
neural  apparatus. 


CHAPTER  IV 

THE  DIFFERENT  TYPES  OF  PERISTALTIC 
ACTIVITY 

BEFORE  taking  up  the  problem  of  peristalsis  it  will 
probably  be  helpful  to  review  briefly  the  different 
types  of  contraction  which  appear  in  different  parts 
of  the  digestive  tract.  We  can  do  this  systematically  by 
following  the  progress  of  a  barium  meal  from  the  mouth  to 
the  anus.  The  mouthfuls  shoot  through  the  first  part  of  the 
esophagus  largely  because  the  muscle  there  is  striated  and 
quick-acting.  In  the  lower  third,  the  muscle  is  largely  of  the 
smooth  variety  and  progress  is  slowed.  Not  infrequently 
powerful  contractions  near  the  cardia  can  be  seen  to  throw 
the  food  back  towards  the  mouth. 

In  the  human  stomach,  waves  appear  about  once  in  twenty 
seconds.  As  will  be  shown  in  Chapter  VIII,  carefully  taken 
serial  plates  reveal  the  fact  that  these  waves  begin  near  the 
cardia.  They  travel  as  shallow  ripples  until  either  proper 
pressure  conditions  or  the  presence  of  the  peculiar  antral 
muscle  causes  them  to  break  into  deep  waves.  Ordinarily 
we  see  only  one  or  two  waves  at  a  time,  but  in  the  presence 
of  a  diseased  gallbladder  or  an  ulcerated  duodenum  the 
stomach  often  gets  so  irritable  that  four  or  five  deep  waves 
course  over  it  at  one  time.  Reverse  waves  are  seen  only 
under  pathological  conditions.  During  the  first  stages  of 
starvation  there  appear  the  powerful,  so-called  hunger 
contractions  (Carlson96) . 

21 


22    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

The  gastric  waves  do  not  cross  the  pylorus  so  far  as  we 
can  see.  As  I  shall  point  out  later,  there  is  some  evidence 
that  an  impulse  or  wave  of  some  kind  does  cross  over  to  give 
rise  perhaps  at  times  to  the  peristaltic  rushes  in  the  small 
bowel.  This  block  seems  to  be  due  partly  to  the  anatomical 
peculiarities  of  this  region  (Cunningham,123  Brinton,73 
p.  268)  and  partly  to  the  physiological  differences  which,  as 
we  shall  see  later,  exist  between  the  muscle  in  the  pyloric 
antrum  and  in  the  duodenum.  According  to  Aufschnaiter,25 
the  circular  muscle  of  the  stomach  thickens  at  the  pylorus 
to  form  a  swelling  in  which  the  little  bundles  of  fibers  are 
more  or  less  braided.  This  swelling  is  divided  into  a  number 
of  sections  by  connective-tissue  partitions  running  from  the 
peritoneum  to  the  mucous  membrane.  One  of  these  partitions 
is  so  complete  that  there  is  little  muscular  connection  left 
between  the  stomach  and  the  duodenum.  Most  of  the  fibers 
in  the  outer  longitudinal  layer  of  the  stomach  dip  down  into 
the  pyloric  swelling,  and  only  a  few  run  over  on  to  the 
duodenum.  Toldt428  believes  l;hat  these  partitions  of  con- 
nective tissue  and  longitudinal  muscle  are  remnants  left 
behind  during  embryonic  life  when  the  pyloric  swelling  is 
formed  by  an  infolding  of  the  wall  of  the  primitive  gut.  A 
few  of  the  circular  fibers  from  the  pyloric  ring  run  down 
over  the  duodenal  cap  in  a  festoon-like  arrangement,  some 
of  them  becoming  almost  longitudinal  in  direction.  The 
connective  tissue  barriers  at  the  pylorus  have  been  des- 
cribed by  one  or  two  other  anatomists  (Todd,427  p.  84)  and 
they  may  easily  interfere  with  the  passage  of  waves.  We 
shall  see  later,  however,  that  gastric  and  intestinal  waves 
can  jump  connective  tissue  gaps  resulting  from  operations, 
so  it  seems  to  me  that  the  main  cause  of  the  block  must  be 
the  difference  in  the  physiological  properties  of  the  muscle 
in  the  stomach  and  in  the  duodenum.  Lillie268  (p.  177)  and 


TYPES  OF  PERISTALTIC  ACTIVITY  23 

again266  (p.  439)  and  others  have  pointed  out  that  a  stimulus 
suited  to  the  metabolism  of  a  sluggish  muscle  will  often  have 
no  effect  on  a  quick-acting  one,  and  it  may  be  that  waves 
coming  every  twenty  seconds  cannot  spread  well  into  a  tissue 
which  contracts  rhythmically  with  a  period  of  three  sec- 
onds. There  is  still  another  possibility,  and  that  is  that  the 
greater  irritability  of  the  sphincteric  muscle  causes  it  to  con- 
tract and  to  get  into  a  refractory  condition  before  the  main 
part  of  the  wave  gets  to  it.  There  is  a  great  deal  of  evid- 
ence to  show  that  a  wave  of  electrical  disturbance  travels 
ahead  of  the  visible  contraction  wave;  and  time  and  again 
while  watching  gastric  peristalsis  in  animals  and  in  man  it 
has  seemed  to  me  that  the  irritable  pyloric  ring  responded 
sufficiently  ahead  of  time  so  that  it  served  to  block  the 
oncoming  wave. 

The  duodenal  cap  tends  to  remain  filled  during  the  early 
stages  of  digestion.  This  may  be  due  to  the  low  rhythmicity 
of  the  muscle  in  that  region  (Alvarez,10  p.  344),  to  its  thinness 
and  weakness  (in  man),  to  its  jirm  attachment  to  the  mucous 
membrane,  and  perhaps  to  the  peculiar  festoon-like  arrange- 
ment of  the  fibers  mentioned  in  the  preceding  paragraph 
(Aufschnaiter,25  Verson438).  Particularly  towards  the  close  of 
gastric  digestion  there  is  normally  some  regurgitation  of 
duodenal  contents  into  the  stomach.  Once  past  the  cap,  the 
food  runs  rapidly  through  the  rest  of  the  duodenum  and 
jejunum.  The  jejunum  is  jejune  or  empty  probably  on 
account  of  its  great  irritability.  The  barium  mixture  in 
that  part  of  the  bowel  moves  so  rapidly  that  it  appears 
to  be  sprayed  over  the  folds  of  the  mucous  membrane. 
In  the  lower  ileum  its  progress  is  slowed  and  the  barium 
meal  can  be  seen  lying  quietly  in  dense  sausage  shaped 
masses. 

We  see  from  time  to  time  in  the  small  bowel,  and  particu- 


24     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

larly  in  the  jejunum,  rhythmic  movements  which  serve  to 
mix  the  food  intimately  with  the  digestive  juices  and  to 
move  it  back  and  forth  over  the  absorbing  surface.  If  these 
contractions  are  spaced  two  or  three  centimeters  apart  we 
have  what  Cannon  calls  "rhythmic  segmentation"  (Fig.  2). 
That  is  seen  often  in  the  cat,  and  I  have  observed  it  also  in 
man.  (See  also  Kastle  and  Bruegel.223)  In  the  rabbit  and  also 


FIG.  2. — A  photograph  of  the  small  intestine  during  rhythmic  segmentation. 

(From  Cannon.) 

in  man  the  contractions  may  appear  five  or  ten  centimeters 
apart,  and  the  food  is  then  thrown  rhythmically  from  one 
end  of  a  short  loop  to  the  other — " Pendelbewegung"  or 
pendulum  movement;  also  " Mischbewegung"  or  "Knetbewe- 
gung."  These  kneading  movements  are  brought  about  by 
local  conditions  of  tension,  and  they  have  little  to  do  with 
the  forwarding  of  food  down  the  bowel.  Experiments  on 
dogs  with  Nella's  fistulae  show  that  they  will  move  material 
at  the  rate  of  one  centimeter  in  from  a  minute  to  an  hour 
(Cash,108  Fubini156).  Most  of  the  forwarding  is  brought  about 
by  the  " Rollbewegungen"  " Schubbewegungen,"  "Forder- 
ungsperistaltik,"  or  "peristaltic  rushes"  which  appear  from 
time  to  time.  These  may  seem  to  arise  in  any  part  of  the 


TYPES  OF  PERISTALTIC  ACTIVITY  25 

small  bowel  and  may  run  either  short  or  long  distances. 
In  diarrheic  rabbits  I  have  seen  them  go  from  the  duodenum 
to  the  anus.  My  graphic  records  show,  however,  that  even 


FIG.  3. — Tracing  from  six  recorders  on  a  rabbit's  small  intestine.  The 
amplitude  of  contractions  is  small  in  the  duodenum.  A  diastaltic  wave  may  be 
observed  in  its  progress  from  one  end  of  the  small  intestine  to  the  other. 
Time  markings  show  thirty-second  intervals.  The  figures  at  the  right  represent 
distances  from  the  pylorus,  in  centimeters. 


the  short  rushes  which,  so  far  as  the  eye  can  see,  have  arisen 
in  the  lower  ileum,  are  generally  based  upon  ripples  which 
have  come  from  the  duodenum  (Alvarez3 — Fig.  3).  As 


26     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

some  of  these  ripples  can  be  shown  to  have  left  the 
first  portion  of  the  duodenum  just  after  a  gastric  wave 
reached  the  pylorus,  it  may  easily  be  that  they  had  their 
origin  as  high  as  the  stomach.  In  a  few  instances  they  fol- 
lowed closely  on  swallowing  movements,  which  suggests 
that  their  origin  may  be  even  higher  than  the  stomach. 
(See  also  Esslemont.143)  The  graphic  records  show  also  that 
the  emptying  of  the  small  bowel  into  the  large,  and  often 
the  defecation  movements  are  timed  by  the  arrival  of  the 
ripples. 

These  rush  waves  serve  to  move  onward  the  material 
which  has  been  segmented  rhythmically  for  some  time  at 
one  point.  Often  as  one  bolus  moves  forward  another  moves 
down  to  take  its  place,  much  as  the  players  in  a  baseball 
game  shift  when  the  bases  are  full  and  the  man  on  third 
goes  "home."  The  rush  waves  tend  to  be  stopped  by  active 
contractions  which  appear  ahead  of  them.  If  this  were  not  so 
the  bowel  would  rapidly  be  emptied,  and  the  animal's 
nutrition  would  suffer. 

The  slowing  of  the  intestinal  contents  above  the  ileocecal 
sphincter  is  due  partly  to  a  tendency  towards  reverse  peristal- 
sis in  that  region  (Alvarez,2  also3).  In  the  rabbit,  the  reverse 
waves  arise  in  the  sacculus  rotundus,  a  rudimentary  cecum 
surrounding  the  sphincter;  in  the  cat,  and  probably  in  man, 
they  arise  in  a  sort  of  accessory  sphincter:  a  thickening  of 
the  last  few  centimeters  of  the  muscular  coat  of  the  small 
intestine  (Luschka,283  Keith,229  Elliott,136  p.  158).  Its  action 
is  much  like  that  of  certain  muscular  rings  which  take  the 
place  of  tight  sphincters  in  lower  forms  of  life  (Bottazzi,67 
p.  481,  and  von  Briicke,75  p.  202).  Were  it  not  for  this 
mechanism  the  food  would  probably  be  rushed  into  the 
colon  too  rapidly.  It  must  not  be  forgotten,  then,  that  the 
sphincter  has  two  functions;  one  to  restrain  the  material 


TYPES  OF  PERISTALTIC  ACTIVITY  27 

coming  down  from  above,  and  the  other  to  prevent  regurgita- 
tion  of  colonic  contents  into  the  ileum. 

Hurst203  (p.  54)  noticed  years  ago  that  after  stagnating  for 
some  time  above  the  sphincter,  the  ileal  contents  tend  to 
empty  into  the  colon  immediately  after  the  taking  of  food. 
I  have  observed  this  "  gastrocolic "  reflex  many  times. 
Lyman284  has  described  a  "receptive  relaxation"  of  the 
colon  for  ileal  emptying  similar  to  that  of  the  stomach  when 
food  is  coming  down  the  esophagus  (Cannon86). 

In  all  this  discussion  I  have  used  the  term  "sphincter" 
instead  of  "valve"  because  it  seems  to  me  that  even  in  man 
the  closure  is  due  mainly  to  a  muscular  puckering.  Ruther- 
ford380 and  others  who  have  been  able  to  observe  the  human 
sphincter  through  large  cecaj  fistulae  maintain  that,  when 
in  action,  there  is  no  sign  of  the  lips  which  appear  in  dis- 
sections; instead,  there  is  a  symmetrical  rosette.  We  know 
that  the  lip-like  structure  is  not  essential  to  health  because 
people  get  along  very  well  after  ileocolonic  anastomoses 
which  are  often  made  very  crudely.  We  know  also  that  the 
bear,  ferret  and  hedgehog  get  along  perfectly  without  any 
sign  of  an  ileocecal  sphincter  (Elliott136). 

The  spontaneous  regurgitation  of  colonic  contents  is 
observed  very  rarely  in  man,  but  it  is  quite  commonly 
observed  after  the  giving  of  barium  enemas  (Dietlen,128 
Case,104  pp.  45,  and,106  pp.  380  and  383).  Although  in 
some  of  these  cases  it  indicates  disease,  it  is  probably  more 
often  due  to  the  abnormal  conditions  brought  about  by  the 
unusual  distention  of  the  colon.  Cannon,86  (p.  156)  found 
in  cats  that  large  enemas  were  passed  back  into  the  small 
intestine  while  small  ones  were  not.  In  this  connection  it  is 
interesting  to  quote  Senn's396  (p.  224)  statement  that  air 
under  a  pressure  of  2%  pounds  per  square  inch  can  be 
passed  from  the  anus  to  the  mouth  in  man. 


28     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

The  physiologist  must  be  interested  also  in  the  fact  that 
the  waves  in  the  ileum  and  in  the  colon  tend  to  stop  at  the 
sphincter.  In  trying  to  explain  this  blockage  we  can  turn  to 
the  same  three  arguments  used  in  the  discussion  of  the 
pyloric  block.  Here  again  we  have  a  certain  amount  of 
plication  and  interruption  of  the  muscular  coats — apparently 
not  so  marked  as  at  the  pylorus.  Engelmann  and  Van 
Brakel141  and  Verson438  speak  of  a  connective  tissue  barrier, 
but  the  illustrations  of  Rutherford380  do  not  show  it.  Toldt428 
shows  that  a  layer  of  longitudinal  muscle  from  the  ileum 
runs  out  nearly  to  the  tip  of  each  valve  lip  between  the  two 
layers  of  circular  muscle,  one  of  which  comes  from  the  ileum 
and  the  other  from  the  colon.  (SeealsoLuschka283andLebon 
and  Auburg.256)  There  is,  moreover,  a  difference  in  the  type 
of  muscle  above  and  below  the  sphincter,  similar  to  that 
above  and  below  the  pylorus.  There  is  also  the  sphincteric 
muscle  which,  probably  on  account  of  a  greater  irritability, 
contracts  in  front  of  and  blocks  advancing  waves  of  reverse 
peristalsis  in  the  colon.  In  the  rabbit  I  have  often  seen  strong 
peristaltic  rushes  crossing  from  the  ileum  to  the  colon  with- 
out any  delay  at  the  sphincter.  Ordinarily,  however,  even 
the  rush  waves  stop  in  the  terminal  ileum.  Heile183  has 
observed  that  stimulation  of  the  colon  will  slow  the  passage 
of  material  through  the  sphincter. 

There  is  one  more  peculiarity  of  the  muscle  in  both  the 
pyloric  and  ileocecal  rings  and  that  is  that  it  contracts  under 
the  influence  of  adrenalin  (Elliott,136  p.  157,  also,137  p.  416; 
and  Kuroda246).  Gaskell160  (p.  46)  has  offered  an  interesting 
explanation  of  this  unique  behavior;  and  it  may  be  that  the 
inclusion  of  these  peculiar  rings  of  muscle  has  something  to 
do  with  the  blocks  in  their  neighborhood. 

The  muscle  in  the  colon  is  sluggish  and  waves  of  contrac- 
tion appear  only  at  long  intervals.  In  the  rabbit  the  haustra 


TYPES  OF  PERISTALTIC  ACTIVITY  29 

show  a  fairly  rapid  and  peculiar  type  of  rhythmic  contraction 
which  I  can  only  liken  to  the  weaving  movements  of  the  two 
jump-ropes  used  by  children.  The  wave  coming  from  the 
left  margin  (as  one  looks  at  a  haustrum)  moves  clockwise 
and  the  one  from  the  right  edge  moves  anticlockwise. 
While  watching  these  movements  one  is  made  to  think  also 
of  the  roll  tops  of  two  desks  facing  each  other.  First  one  top 
is  pulled  down  and  then  the  other.  Hurst  and  Newton205 
claim  to  have  seen  similar  movements  in  man,  but  they 
must  certainly  be  rare.  Kastle  and  Bruegel223  took  cine- 
matographic plates  of  the  colon  in  man  and  observed  very 


FIG.  4. — Photograph  of  a  colon  exposed  under  warm  salt  solution.  Tonus 
ring  6  is  sending  forth  antiperistaltic  waves,  which  are  stopped  by  the  nearly 
relaxed  tonus  ring  a.  (From  Cannon.) 

little  movement.  They  describe  several  types  of  slow  haus- 
tral  contractions.  In  man,  forwarding  movements  appear 
probably  only  a  few  times  a  day.  These  were  described 
by  Hurst  in  ipoy197  (p.  423)  and  in  ipoS198  (p.  9);  Holz- 
knecht192  in  1909;  by  Barclay32  in  1912,  and  later  by  Hurst 
and  Newton,205  Case106  (1915),  and  others.  I  have  seen  them 
several  times,  generally  in  people  with  a  tendency  to  diarrhea. 
The  haustra  relax,  a  sausage-shaped  mass  is  formed,  usually 
in  the  transverse  colon,  and  this  is  rushed  quite  rapidly 


30     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

toward  the  rectum.  In  the  cat  and  dog,  defecation  is  brought 
about  ordinarily  by  a  marked  shortening  and  a  powerful  con- 
traction of  almost  the  whole  colon;  in  man  the  process  is 
confined  almost  entirely  to  an  emptying  of  the  sigmoid  and 
rectum. 

Reverse  peristalsis  is  a  normal  activity  in  the  right  half  of 
the  colon  in  a  number  of  animals  (Sanders,382  Jacob;,212 
p.  147;  Cannon,86  p.  152  and80,  p.  265 — Fig.  4).  It  has  been 
observed  in  man  (Case,104  and,107  p.  687,  but  there  it  is  hard 
to  demonstrate;  and  the  waves  certainly  do  not  correspond 
in  activity  and  depth  to  those  seen,  for  example,  in  the 
cat.  Kastle  and  Bruegel223  could  not  show  it  in  their  cine- 
matographic studies.  As  Cannon  has  shown  so  beautifully, 
the  reverse  waves  in  animals  often  start  from  a  pulsating 
contraction  ring.  They  run  for  a  while,  and  then  alternate 
with  downward  waves. 

Reverse  transport  of  material  is  observed  not  infrequently 
in  the  lower  colon  when  defecation  is  postponed  (Schwartz,394 
Case106).  Under  those  conditions  feces  may  move  back  into 
the  sigmoid  or  descending  colon.  The  reverse  transport 
of  material  in  the  colon  after  ileosigmoidostomy  is  now  well 
known. 

SUMMARY 

The  point  that  I  wish  to  emphasize  in  the  foregoing 
discussion  is  that  there  are  several  types  of  intestinal  move- 
ment— types  which  must  be  distinguished  clearly  or  mis- 
understandings will  arise.  They  may  be  recapitulated 
briefly  as  follows: 

Stomach — Regularly  recurring  waves  running  from 
cardia  to  pylorus.  Reverse  peristalsis  pathologic. 

Small  Intestine — Rhythmic  segmenting  or  kneading 
movements  which  have  little  to  do  with  forwarding  the 


TYPES  OF  PERISTALTIC  ACTIVITY  31 

contents.  Occasional  rush  waves  which  move  food  for 
shorter  or  longer  lengths  through  the  bowel.  Reverse 
peristalsis,  probably  pathologic,  except  towards  the  close 
of  gastric  digestion  when  duodenal  contents  normally 
regurgitate  into  the  stomach.  Perhaps  some  normal  reverse 
peristalsis  in  the  terminal  ileum. 

Colon — Sluggish  local  contractions  and  haustral  move- 
ments. Rush  waves  at  long  intervals.  Reverse  peristalsis 
physiologic,  particularly  in  the  right  half  of  the  colon. 

Cannon  and  others  have  invented  the  following  names 
for  these  different  manifestations: 

Peristalsis — A  general  term  for  intestinal  movements. 

Katastalsis — Normal  downward  movements  in  stomach 
or  colon. 

Diastalsis — Through-  or  rush-waves  in  the  small  bowel. 

Anastalsis  or  Retrostalsis — Reverse  peristalsis. 

If  the  stomach  is  cut  out  and  put  in  a  warm  moist  chamber 
or  in  Locke's  solution,  waves  may  go  over  it  just  as  they 
do  in  the  intact  animal.  If  a  loop  of  small  intestine  is  simi- 
larly treated,  rhythmic  contractions  appear  now  here,  now 
there  along  its  length.  One  part  does  not  set  the  pace  for 
another,  and  only  rarely  can  one  see  waves  traveling  from 
one  end  of  the  loop  to  the  other.  If  a  short  segment  is 
fastened  to  a  little  lever  it  will  contract  regularly  at  a 
rate  which  corresponds  to  that  of  the  rhythmic  segmenta- 
tion in  the  region  from  which  the  piece  was  removed.  That 
rate  varies  inversely  as  the  distance  from  the  pylorus. 

In  the  discussion  which  makes  up  most  of  this  book  I  shall 
be  concerned  mainly  with  the  diastaltic  and  anastaltic  types 
of  waves  which  move  food  from  one  end  of  the  stomach  or 
bowel  to  the  other. 


CHAPTER  V 
GRADIENTS 

IF,  at  a  certain  point,  we  stimulate  the  smooth  muscle  in  a 
tubular  organ  like  the  intestine  or  ureter,  we  get  a  con- 
tracted tonic  ring  from  which  waves  are  given  off  in  both 
directions  (Cannon,84  and,87  p.  419;  Engelmann,140  p.  259; 
Kretschmer243).  These  waves  remind  one  of  the  concentric 
ripples  which  arise  at  the  point  where  a  stone  has  been 
thrown  into  a  pond,  and  actually  the  physical  conditions 
underlying  the  two  phenomena  are  very  similar.  In  each 
case  the  level  or  potential  is  raised  at  one  point  and  waves 
of  activity  flow  down  away  from  that  region  until  an  equili- 
brium is  restored.  If  another  stone  is  thrown  into  the  pond 
near  the  first  one,  some  of  the  waves  approaching  the  second 
area  are  slowed  and  stopped;  and  similarly,  if  a  second 
tonus  ring  is  made  in  the  bowel,  the  waves  approaching  it  are 
blocked.  They  are  slowed  and  stopped  because  they  have,  in 
a  way,  to  run  up  hill  to  the  second  area  of  high  potential. 
One  of  the  best  ways  in  which  to  make  one  of  these  pulsating 
contraction  rings  is  to  touch  the  bowel  with  a  crystal  of 
barium  chloride  which,  as  is  well  known,  raises  the  tone  of  the 
muscle. 

CONDUCTION.  These  waves  spread  out  from  muscle  fiber 
to  muscle  fiber,  and  there  is  little  need  for  any  assistance 
from  nerves,  ganglia  or  centers.  I  have  observed  such  waves 
(after  electrical  stimulation)  spreading  both  ways  along  the 
segments  of  a  recently  voided  c&g's  tapeworm,  and  I  have 

32 


GRADIENTS  33 

seen  them  traveling  away  from  the  ridge  which  forms  when 
one  strikes  the  irritable  pectoral  muscles  of  a  consumptive; 
yet  in  neither  of  these  tissues  is  there  anything  corresponding 
to  Auerbach's  plexus.  Cannon86  (p.  193)  has  shown  that 
peristaltic  waves  continue  to  travel  over  the  stomach  after 
it  has  recovered  from  the  making  of  several  cuts  through  the 
muscle  and  plexus  down  to  the  mucous  membrane;  and 
Meek316  has  made  similar  observations  on  the  bowel.  Appar- 
ently when  a  wave  approaches  one  of  the  scar  tissue  barriers 
it  pulls  on  the  muscle  on  the  other  side;  it  stretches  that 
muscle  and  thereby  produces  a  contraction.  Conditions  are 
analogous  perhaps  to  those  in  Friedlander's155  (p.  366) 
experiment  in  which  he  cut  an  earthworm  in  two  and  tied 
the  pieces  together  with  a  bit  of  thread.  The  hind  end 
crawled  in  coordination  with  the  front  end  because  the 
pull  on  the  skin  was  a  sufficient  stimulus  for  the  underlying 
muscles. 

There  is  yet  another  way  in  which  waves  may  spread  from 
fiber  to  fiber  or  across  connective  tissue  barriers,  and  that  is 
by  means  of  the  electric  action-currents.  It  is  well  known  that 
when  a  muscle  contracts  or  a  nerve  conducts  a  small  and 
transitory  current  is  formed.  This  always  runs  in  a  circuit 
from  the  active  place  through  the  tissue  to  the  resting  place 
and  back  again  through  the  surrounding  medium.  It  has 
long  been  suspected  that  these  action  currents  might  lead  to 
a  progression  of  activity  by  stimulating  the  tissue  just 
beyond  the  active  place;  arid  in  recent  years,  largely  through 
the  efforts  of  R.  S.  Lillie,  that  view  has  become  strengthened 
almost  to  a  certainty.  Two  of  his  interesting  observations 
are  worth  quoting  at  this  point.  In  the  ctenophores,  there 
are  rows  of  swimming  plates  or  large  cilia  which  beat  in 
order,  so  that  waves  of  movement  run  from  one  end  to  the 
other.  If  one  of  these  rows  is  cut  off  and  left  for  a  while  in 


34     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

sea  water,  it  curls  up  so  that  the  two  ends  are  brought 
within  a  few  millimeters  of  each  other.  It  frequently  happens 
then  that  the  wave  of  ciliary  motion- jumps  the  gap  between 
the  ends  and  goes  on,  so  that  a  wave  of  activity  runs  around 
the  ring  for  hours  at  a  time.  Similarly,  if  a  large  number  of 
spermatozoa  of  the  annelid  Nereis  are  allowed  to  stand  in  a 
watch  crystal  they  tend  to  form  layers  and  to  contract 
rhythmically  in  unison.  With  the  waves  of  activity  going 
back  and  forth  they  give  the  picture  of  a  layer  of  ciliated 
epithelium  (Lillie,266  p.  428).  In  these  two  experiments  there 
can  be  little  question  as  to  the  mode  of  transmission  across 
the  liquid  medium;  and  certainly  nerves  have  nothing  to  do 
with  it.  Again  I  find  myself  emphasizing  the  independence 
of  the  muscle  as  regards  nervous  assistance,  not  because  I 
think  the  nerves  are  without  function,  but  because  I  wish 
my  readers  to  pay  more  attention  to  the  graded  peculiarities 
of  the  muscle  and  to  the  workings  of  ordinary  physical 
laws. 

Returning  again  to  the  simile  of  waves  spreading  in  water, 
it  seems  to  me  that  some  tubular  organs  may  be  likened  to 
ponds  which  are  level  to  begin  with;  others  are  more  like 
rivers  which  have  definitely  established  gradients.  In  the 
first  case,  the  waves  spread  equally  well  in  all  directions;  in 
the  second,  the  waves  spread  more  easily  downstream  than 
up.  Perhaps  I  can  illustrate  this  point  best  by  showing  the 
evolution  of  the  fixed  gradient  in  the  heart.  As  is  well  known, 
in  that  organ  the  beat  follows  a  gradient  of  rhythmicity 
from  the  sinus  to  the  ventricle.  It  was  Gaskell158  who  first 
pointed  out  that  "the  rhythmical  power  of  each  segment  of 
the  heart  varies  inversely  as  its  distance  from  the  sinus." 
Thus,  if  we  cut  a  heart  into  three  or  four  pieces,  the  one 
containing  the  mouths  of  the  great  veins  will  show  the 
greatest  tendency  to  beat  rhythmically,  and  it  will  have 


GRADIENTS  35 

the  fastest  rate;  the  ventricle  will  be  slow  to  start  beating 
and  it  will  have  a  slow  rate.  If,  however,  we  turn  to  the 
primitive  heart  of  the  sea  slug,  aplysia,  we  find  a  tube  which 
apparently  has  no  constant  gradient  in  either  direction.  Its 
beat  arises  now  on  one  side  and  now  on  the  other,  depending 
on  where  the  blood  produces  the  greatest  tension  (Straub,415 
p.  518).  Hunter195  could  find  no  sign  of  a  gradient  in  the 
heart  of  one  of  the  ascidians.  In  these  animals  the  beat  runs 
for  a  while  towards  the  viscera  and  then  for  a  while  towards 
the  gills.  The  pace-making  end  seems  to  get  fatigued;  its 
rate  is  slowed  and  finally  the  other  end  is  able  to  assume  the 
pace  for  a  while.  A  constant  direction  of  contraction  may  be 
maintained  by  electrical  stimulation  of  either  end  of  such 
a  heart  (Bancroft  and  Esterly29).  It  seems  to  me  that 
Hecht's181  studies  on  Ascidia  atra  show  us  the  very  beginning 
of  the  fixed  gradient  which  we  find  in  the  hearts  of  the 
higher  animals.  He  found  that  although  the  heart  of  the 
ascidian  reverses  its  beat  from  time  to  time,  the  sum  of 
the  advisceral  beats  is  about  twice  that  of  the  abvisceral. 
Moreover,  as  we  should  expect,  if  the  gradient  is  a  little 
better  in  the  advisceral  direction,  the  rate  of  conduction  is 
definitely  faster  in  that  direction  than  in  the  other.  If  a  wave 
is  started  in  the  middle  of  the  heart,  going  both  ways,  it 
tends  to  efface  the  abvisceral  waves,  which  according  to  our 
theory  would  have  the  smaller  momentum.  It  is  interesting 
also  that  under  slightly  adverse  conditions,  as  after  warming 
the  water,  or  after  diluting  or  concentrating  it,  it  is  the 
abvisceral  beat  which  is  suppressed.  We  find  a  little  more 
stable,  but  still  reversible  heart  beat  in  the  sharks  and  rays 
(Bottazzi,69  p.  372;  Gaskell,159  p.  184).  In  them  the  slightest 
stimulus  to  the  bulbus  aortae  will  reverse  the  beat  and  the 
same  stimulus  to  the  sinus  will  restore  it.  Even  in  the  higher 
vertebrates  the  heart  beat  can  be  reversed  temporarily  by 


36     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

agencies  which  lower  the  rhythmicity  of  the  auricle  or  raise 
that  of  the  ventricle  (Eyster  and  Meek146).  Ordinarily, 
however,  as  we  have  seen,  the  beat  arises  in  the  sinus  region 
and  keeps  coming  from  there  because  that  area  has  the 
greatest  rhythmicity  and  the  fastest  inherent  rate. 

GRADIENTS  IN  OTHER  ORGANS.  There  is  considerable 
evidence  now  that  peristalsis  in  the  ureter  follows  a  gradient 
of  rhythmicity  from  the  kidney  to  the  bladder  (Penfield,358 
Lucas,275  SokoIofF  and  Luchsinger,405  Satani,383  Wislocki 
and  O'Connor449)..  I  have  done  considerable  work  with 
excised  segments  of  ureter  and  have  found  that  the  rate 
of  rhythmic  contraction  is  often  fastest  in  the  piece  removed 
from  the  kidney  end.  This  gradient  is  not  so  constant  or 
so  marked  as  it  is  in  the  bowel.  I  have  other  records  from 
segments  of  Fallopian  tubes  and  vas  deferens  which  suggest 
strongly  that  there  are  similar  rhythmic  gradients  in  those 
tubes.  We  may  perhaps  later  be  able  to  state  it  as  a  general 
physiologic  law  that  the  direction  of  transport  of  material 
in  a  tubular  organ  depends  upon  gradients  of  rhythmicity, 
tone  and  irritability.  When  we  come  to  think  of  it,  our 
experience  with  engineering  and  physics  should  have  led  us 
long  ago  to  look  for  gradients  in  these  muscular  tubes. 
We  know  that  water  in  a  pipe  follows  gradients  of  gravity 
or  of  pumping  pressure;  electricity  flows  along  gradients 
of  electro-motive  force,  the  winds  follow  gradients  of  baro- 
metric pressure,  etc.  Moreover,  anyone  who  has  ever  tried 
to  milk  a  cow  knows  that  it  is  not  hard  squeezing  which 
brings  results,  but  a  coordinated,  graded  contraction  begin- 
ning at  the  top  of  the  teat  and  working  down  to  the  end. 

GRADIENT  IN  THE  INTESTINE.  What  evidence  have  we 
now  that  there  is  a  gradient  in  the  gastro-intestinal  tract? 


GRADIENTS  37 

So  far  as  rhythmicity  goes  the  evidence  is  overwhelming. 
It  is  a  simple  thing  to  open  an  animal  under  salt  solution 
and  to  demonstrate  that  the  rate  of  rhythmic  contraction 
varies  from  about  twenty  per  minute  in  the  duodenum 
to  ten  per  minute  in  the  lower  ileum  (Alvarez,3  Fig.  3). 
It  is  easy  also  to  cut  out  short  segments  of  the  bowel  and 
to  show  that  their  rate  of  rhythmic  contraction  continues 
to  vary  inversely  as  the  distance  from  the  pylorus  (Alvarez,2 
and,10  Fig.  5).  A  similar  gradient  can  be  shown  in  strips  of 
muscle  excised  from  the  wall  of  the  stomach  (Alvarez,5 
Fig.  10).  There  the  fastest  rate  is  found  in  the  strip  from  the 
lesser  curvature  near  the  cardia.  It  is  harder  to  show  the 
gradient  in  the  colon  (Alvarez  and  Starkweather17)  but  that 
was  to  be  expected  when  we  remember  that  the  large  bowel  is 
more  sluggish  than  the  small;  it  lets  the  contents  lie  in  one 
place  for  long  periods  of  time  and  it  often  shows  reverse 
peristalsis.  Hence  it  is  that  the  excised  piece  is  slow  to  start 
beating;  its  rate  is  slow;  it  tends  to  contract  down  into  a  hard 
knot  and  stay  that  way,  and  the  gradient  is  poor  and  often 
reversed.  In  the  small  intestine  of  the  rabbit  and  white  rat 
the  rhythmic  gradient  is  so  fixed  and  so  intimately  "built 
into"  the  structure  of  the  intestine  that  one  can  determine 
the  oral  and  aboral  ends  of  short  excised  segments  by 
counting  the  rates  at  the  two  ends. 

REVERSAL  EXPERIMENTS.  It  has  always  seemed  to  me  that 
the  gradient  is  more  stable  in  the  rabbit,  guinea  pig  and  rat 
than  in  the  cat  and  dog,  perhaps  because  the  first  three 
have  long  thin  intestines  and  bulky  food,  while  the  last  two 
have  short,  strong-walled  ones  and  nfore  concentrated  food. 
As  will  be  seen  shortly,  the  gradient  must  be  well  es- 
tablished if  rough  solid  particles  of  food  are  to  be 
passed  on.  If  we  think  of  the  bowel  as  a  pipe  line,  with 
uphill  stretches  in  it,  we  know  that  water  can  be  forced 


38    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

through  such  stretches,  but  not  rocks.  Similarly,  if  we  take 
dogs,  cut  out  sections  of  their  small  intestines,  turn  them 
end  for  end  and  anastomose  them  again,  we  can  keep 
the  animals  alive  for  months  if  the  greatest  care  is  taken 


FIG.  5. — To  show  the  difference  in  the  rate  of  rhythmic  contraction  in  the 
excised  segments.  Note  also  the  graded  recovery  from  pilocarpin  after  adding 
atropin.  From  above  downward,  the  records  are  from  duodenum,  upper 
ileum,  lower  ileum  and  colon.  Time  record  represents  thirty  seconds. 

to  keep  rough  and  indigestible  foods  from  them.  Eventu- 
ally they  die  from  intestinal  obstruction,  and  autopsy 
shows  that  bits  of  straw,  bone,  wood,  etc.,  have  accumulated 


GRADIENTS  39 

at  the  upper  suture  and  have  finally  blocked  the  lumen 
(Kirstein,237  Mall,299  p.  93;  Kelling,233  Miihsam,331  Enderlen 
and  Hess,139  Prutz  and  Ellinger,365  and  366;  Beer  and  Eggers,44 
McCIure  and  Derge,312  Cannon,86  p.  142).  (Fig.  6.)  It  is 
clear  that  the  original  direction  of  peristalsis  remains 
fixed  in  these  loops  and  that  liquids  can  be  forced  through 
when  solids  cannot.  Liquids  can  be  pumped  into  a  normal 
cat's  rectum  until  they  flow  from  her  mouth  (Senn,396 
p.  221),  but  Bayliss  and  Starling39  (p.  106)  found  that  any 
attempt  to  force  a  solid  body  like  a  tampon  on  a  stick 
in  the  orad  direction  through  a  loop  of  living  bowel  was 
likely  to  result  in  severe  trauma  on  account  of  the  great 
resistance  exerted  by  the  muscle.  These  experiments  make 
me  feel  that  the  gradient  must  be  basic  and  not  the  result 
of  functional  adaptation  as  some  might  think.  Further 
evidence  for  that  conclusion  is  found  in  the  fact  that  the 
gradient  is  just  as  marked  in  the  fetal  intestine,  which  has 
not  yet  functioned,  as  in  the  adult  animal  (Alvarez  and 
Starkweather11). 

The  permanence  of  the  gradient  in  the  gut  is  to  be  expected 
from  studies  on  the  lower  forms  of  life.  The  mouth  of 
a  frog  is  lined  by  epithelium  covered  with  little  cilia  which 
wave  in  one  direction.  If  a  piece  of  this  epithelium  is 
cut  out,  turned  through  an  angle  of  180°,  and  grafted 
back  again,  the  cilia  continue  to  beat  in  their  original 
direction,  now  contrary  to  that  in  the  rest  of  the  mouth 
(von  Brucke75).  In  some  of  the  worms  the  so-called  "po- 
larization" is  so  perfect  that  if  the  animal  is  cut  into  many 
small  pieces  they  will  all  crawl  in  the  same  direction  to- 
wards the  point  where  the  head  used  to  be  (Carlson,94 
p.  284;  Biedermann,59  p.  288).  The  early  development  and 
stability  of  these  gradients  of  growth  and  activity  are  well 
shown  by  some  experiments  resembling  those  in  which  the 


40    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

segments  of  intestine  were  reversed.  Hooker193  chiseled  out 
little  segments  from  the  cervical  region  of  the  growing 
spinal  cord  of  frog  embryos;  he  turned  these  pieces  end 
for  end,  and  grafted  them  back  into  place.  The  interesting 


FIG.  6. — Shows  the  results  of  reversing  a  segment  of  dog's  intestine.  Note 
enormous  spindle-shaped  dilatation  on  either  side  of  the  upper  anastomosis. 
A.  The  point  of  greatest  dilatation  is  3  cm.  above  the  suture  on  the  normally 
directed  intestine.  Lower  anastomosis  of  reversed  loop  at  B,  where  lumen 
remains  of  normal  size.  (From  McClure  and  Derge.) 

thing  is  that  the  nerve  fibers  in  the  reverse  segment  con- 
tinued to  grow  in  the  original  direction  in  spite  of  the  great 
force  which  was  exerted  against  them  by  the  growth  of  fibers 
coming  down  from  above.  A  similar  reversal  of  segments 
from  the  duodenal  region  of  tadpoles  produces  si^us  inversus 
in  the  abdominal  organs  (Pressler364). 


GRADIENTS  41 

To  sum  up:  waves  tend  to  spread  out  in  both  directions 
from  a  stimulated  place  on  a  muscular  tube,  as  ripples  spread 
in  a  pond  when  a  stone  is  thrown  in.  If  the  stone  is  thrown 
into  a  river  the  waves  will  travel  downstream  more  easily 
than  up.  Similarly  in  the  heart  and  intestine,  a  gradation  in 
rhythmicity  makes  it  easier  for  the  waves  to  go  in  one 
direction  than  in  the  other.  Actually,  in  the  bowel  Miss 
Starkweather  and  I  found  that  the  effect  of  a  stimulus  could 
be  detected  much  farther  caudad  than  cephalad.18 

A  GRADIENT  OF  FORCE.  Several  years  ago  while  working 
with  a  man  who  had  a  jejunal  fistula  I  found  a  marked  differ- 
ence in  the  pulling  force  exerted  by  different  parts  of  the 
bowel  on  balloons.  The  jejunum  pulled  almost  constantly 
and  with  considerable  strength,  while  the  ileum  pulled  inter- 
mittently and  weakly.  Searching  through  the  literature  I 
found  that  Hess187  had  observed  the  same  thing  in  dogs  with 
gastric  fistulae  through  which  he  could  insert  balloons 
into  the  duodenum.  Eighteen  centimeters  from  the  pylorus 
the  pull  corresponded  to  228  grm.;  20  cm.  farther  down  it  was 
90  grm.;  and  12  cm.  farther  below  that,  it  was  75  grm.  Later, 
Brandl  and  Tappeiner72  worked  out  the  rest  of  the  gradient 
farther  down  the  ileum.  It  is  clear  from  these  experiments 
that  there  is  a  gradient  of  propulsive  force  along  the  bowel 
much  like  that  in  a  pipe  line. 


CHAPTER  VI 

THE   UNDERLYING   BASIS   OF   THE    RHYTHMIC 

GRADIENT 

WE  have  seen  that  there  is  a  rhythmic  gradient  in 
the  bowel  from  the  pylorus  to  the  colon.  The 
next  question  is:  What  is  there  underlying  this 
gradient;  how  did  it  come,  and  how  is  it  kept  up?  Should 
we  not  expect  to  find  anatomic  and  metabolic  gradients 
running  parallel  to  the  rhythmic  one?  Those  who  are  partial 
to  theories  of  neurogenic  origin  will  probably  think  first  of 
looking  for  some  graded  difference  in  the  structure  of  Auer- 
bach's  plexus;  and  actually  such  a  difference  has  been 
found.  Gerlach164  showed  years  ago  that  the  mesh  of  the 
plexus  becomes  coarser  and  the  ganglion  cells  fewer  as  one 
goes  from  the  duodenum  to  the  ileum;  and  more  recently, 
Kuntz245  has  found  a  gradient  in  the  concentration  of  the 
sympathetic  neurones,  from  the  duodenum  to  a  point  about 
12  cm.  above  the  ileocecal  sphincter.  It  seems  to  me,  how- 
ever, that  as  the  evidence  summarized  in  Chapter  II  points 
to  the  myogenic  origin  of  the  rhythmic  movements,  we  must 
not  rest  satisfied  with  these  findings  but  must  look  also 
for  graded  differences  in  the  structure  and  chemical  activity 
of  the  muscle. 

Now,  it  has  been  shown  that  the  rate  of  rhythmic  con- 
traction of  a  muscle  is  dependent  upon  the  rate  at  which  its 
chemical  processes  go  on.  Some  substance  seems  to  be  built 
up  to  a  certain  point  and  then  perhaps  exploded  or  torn 
down  to  produce  the  contraction;  if  the  metabolic  rate  is 

42 


THE  BASIS  OF  THE  RHYTHMIC  GRADIENT       43 

slow  it  should  take  longer  to  complete  the  cycle.  As  Wood- 
worth451  says,  the  rate  of  contraction  seems  to  be  adapted  to 
the  metabolism  of  a  muscle;  "if  the  pause  preceding  ...  is 
too  short,  the  contraction  suffers  from  lack  of  recuperation. 
If  it  is  too  long,  the  contraction  suffers  from  what  we  may 
perhaps  call  a  sort  of  drowsiness. "  We  know  also  that  warm- 
ing hastens  chemical  processes,  and  Magnus289  and  Taylor 
and  Alvarez424  have  shown  that  warming  the  intestine 
hastens  the  rate  of  rhythmic  contraction.  As  we  can  take  a 
piece  of  ileum  beating  10  times  a  minute  and  by  warming  it, 
speed  up  its  metabolism  so  that  it  will  beat  17  times  a 
minute,  it  seems  to  me  that  the  duodenum  which  normally 
beats  17  times  a  minute  probably  has  a  faster  metabolic 
rate  than  the  ileum. 

The  warming  not  only  increases  the  rate  of  contraction, 
but  it  shortens  the  latent  period  and  markedly  alters  the 
form  of  the  contraction  curve.  These  changes  probably 
account  for  de  Zilwa's454  finding  that  with  a  muscle  at 
40°  C.  stimuli  have  to  follow  each  other  at  intervals  of  from 
four  to  ten  seconds  if  summation  is  to  be  obtained.  At  25°  C.  the 
interval  can  be  twenty  seconds  or  more.  Similarly  Engelmann  14° 
while  studying  the  ureter  of  the  rabbit,  found  that  a  series 
of  subliminal  stimuli  might  bring  about  a  contraction  if  the 
interval  between  them  was  not  too  great  for  summation. 
When  the  irritability  was  high  and  the  waves  were  traveling 
rapidly  down  the  ureter,  the  interval  had  to  be  shorter. 
It  had  to  be  shorter  also  when  using  the  ureter  of  the  rat,  as 
there  the  rate  of  the  waves  is  normally  faster  than  in  the 
rabbit.  It  seems  pretty  clear,  then,  that  a  muscle  which  beats 
at  17  per  minute  is  different  from  that  which  beats  at  10  per 
minute.  It  apparently  has  been  constructed  differently  in 
some  way,  so  that  its  chemical  processes  will  go  on  at  a 
faster  rate,  much  as  those  of  a  baby  go  on  faster  than  those  of 


44     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

an  adult.  Those  who  would  like  to  learn  more  about  this 
relation  between  activity  and  metabolic  rate  should  turn  to 
an  interesting  article  by  Miss  Hyman.210  As  she  (Hyman,207 
p.  378)  points  out,  the  word  metabolism  is  generally  taken  to 
signify  the  sum  of  all  the  energy-producing  and  substance- 
producing  processes  occurring  in  the  body;  but  as  the 
oxidative  processes  are  the  most  important  ones  it  is  suffi- 
cient for  our  purposes  to  measure  the  rate  of  respiratory 
exchange.  Child113  (p.  152)  uses  the  word  metabolic  gradient, 
not  because  he  is  satisfied  that  it  is  purely  or  primarily 
metabolic  in  character,  but  because  oxidation  seems  to  be 
the  "fundamental  factor  in  life  and  the  chief  source  of  the 
energy  of  living  organisms  »  ...  Protoplasm  is  a  system 
in  which  the  chemical  reactions  of  metabolism  are  so  inti- 
mately associated  with  other  factors,  e.g.,  colloid  dispersion, 
active  mass  of  enzymes,  permeability  of  limiting  surfaces, 
electrolyte  and  water  content,  etc.,  that  to  attempt  to  distin- 
guish one  particular  factor  ...  as  primary  is  at  present 
impossible.  The  term 'metabolic  gradient'  .  .  .  means  onlv 
that  the  metabolic  factor  is  a  characteristic  feature.  .  .  . 
The  term  'physiologic  gradient'  which  avoids  all  specific 
implications  might  be  substituted  for  it." 

Reasoning  along  these  lines, .  Miss  Starkweather  and 
I11  measured  the  C  O2  production  of  equal  weights  of  muscle 
from  different  parts  of  the  bowel  and  found  a  definite  grad- 
ation from  the  duodenum  to  the  colon.  This  was  true  not 
only  for  the  active  but  also  for  the  resting  muscle.  During 
the  last  three  years  Miss  Starkweather,  Dr.  Taylor  and  I 
have  been  collecting  data  on  the  oxygen  intake  of  the  muscle 
from  different  regions,  and,  as  was  to  be  expected,  that 
appears  to  be  graded  as  is  the  C  O%  output. 

Graded  differences  have  been  found  also  in  the  catalase 
content  of  equal  weights  of  minced  muscle.  There  are  many 


THE  BASIS  OF  THE  RHYTHMIC  GRADIENT       45 

reasons  for  believing  that  this  catalase  is  involved  in  some 
way  in  the  normal  oxidative  processes  of  the  cell,  but  just 
how  we  do  not  know.  It  is  very  suggestive  that  there  is 
considerable  parallelism  between  the  metabolic  rates  of 
many  tissues  and  their  catalase  contents,  but  there  are 


(1)    (2)    (3)    (4)    (5)    (6)    (7) 


16. C 
15.0^.2 

14. C 
13.C13' 
12. C 
11. C 

LO.O 

9. 

8.0 


47.9 


28. 


2.7 
2.5 


0.30 


0.23! 


0.1' 
0.1£ 


B7.921 


(1)  Rabbit,   rate  excised 

(2)  Rabbit,  oatalas* 

(3)  Rat,   C02,    titrated 

(4)  Guinea  pig,    COg 

(5)  Pig  embryo,   oatalaae 

(6)  Oat,  catalase 

(7)  Rabbit,   rate   intact 


D  J  M  * 

FIG.  7. — Showing  the  parallelism  between  the  gradients  of  rhythmic  con- 
traction, CC>2  production  and  catalase  content  in  different  animals.  In  order 
to  bring  the  different  curves  closer  together,  an  arbitrary  set  of  ordinates  was 
chosen  running  from  8  to  16.  The  seven  sets  of  data  were  then  multiplied 
or  divided  by  factors  which  would  place  the  first  figure  for  the  duodenum  be- 
tween 14  and  1 6.  The  original  data  are  shown  as  ordinates  in  the  seven  columns 
on  the  left.  The  numbered  columns  correspond  to  the  numbered  legends 
identifying  the  different  curves.  The  abscissae  represent  the  four  segments 
along  the  gut. 

exceptions  and  many  possibilities  of  error;  and  the  subject  is 
still  under  active  discussion.  Under  the  circumstances  it  can 
be  regarded  only  as  highly  suggestive  that  there  is  a  remark- 
able parallelism  between  the  C  O2  output  and  the  catalase 
content  of  the  muscle  in  the  digestive  tract.  The  similarity 


46     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

of  these  gradients  Is  shown  in  Fig.  7.  It  will  be  helpful  later 
when  we  learn  more  exactly  what  our  data  mean,  because  the 
technique  is  easy  and  the  results  are  generally  clear-cut  and 
striking.  One  thing  is  certain,  and  that  is  that  we  cart  show  a 
definite  chemical  difference  between  the  muscle  in  the 
duodenum  and  that  in  the  ileum  or  colon.  Other  forms  of 
chemical  analysis  would  probably  show  differences  in  com- 
position similar  to  those  found  by  Lee,  Guenther  and 
Meleney258  when  they  compared  the  diaphragm  with  other 
skeletal  muscles. 

Gradients  in  metabolic  rate  have  been  shown  to  exist  in 
many  parts  of  the  body  and  it  seems  to  me  that  their  impor- 
tance in  biologic  studies  is  going  to  be  realized  more  and 
more  as  time  goes  on.  They  appear  at  the  very  beginning  of  \ 
lije  in  the  ovum  and  thereafter  have  much  to  do  in  controll-  J 
ing  the  development  of  the  organism.  Thus  in  the  frog,  that 
part  of  the  egg  which  happens  to  get  the  best  blood  supply 
from  the  ovarian  membrane  forms  the  embryo  (Bellamy46). 
The  most  rapidly  growing  part  of  the  embryo  forms  the 
nervous  system;  and  the  most  rapidly  growing  part  of  the 
nervous  system  .becomes  the  brain.  These  differences  in 
metabolic  rate  show  themselves  as  differences  in  the  rate  of 
cell  division  and  in  the  size  of  the  cells  along  the  future 
axes  of  the  organism.  They  are  found  not  only  in  ova,  but  in 
developing  seeds,  where  the  polarity  is  often  determined  by 
slight  differences  in  illumination  (Child,113  p.  170). 

Once  such  regions  of  rapid  growth  are  established,  their 
activity  serves  to  regulate  and  hold  in  check  the  growth  of 
other  parts  of  the  developing  animal  or  plant.  This  control 
can  easily  be  demonstrated  by  cutting  off  or  impairing  the 
growth  of  the  tip  of  an  evergreen  tree,  or  the  head  of  a 
primitive  type  of  animal  like  a  hydroid  or  a  planarian  worm. 
In  the  simplest  organisms  there  is  only  the  apico-basal 


THE  BASIS  OF  THE  RHYTHMIC  GRADIENT      47 

pattern  with  its  corresponding  gradient,  but  in  higher  forms 
with  lateral  symmetry  there  are  radial  gradients  running 
at  right  angles  to  the  longitudinal  or  polar  ones  (Child113). 
Thus  in  certain  algae  and  in  trees  there  is  a  metabolic 
gradient  along  the  main  trunk  from  the  rapidly  growing  tip 
to  the  roots  and  there  are  other  gradients  in  the  branches 
from  the  tips  to  the  trunk.  It  is  a  remarkable  thing  that  in 
some  plants  and  lower  animals  these  original  gradients  can 
be  effaced,  altered  or  reversed  either  accidentally  or  experi- 
mentally: and  with  the  change  in  gradient  goes  a  change  in 
the  structure  of  the  animal.  Thus  a  piece  of  a  planarian 
worm  may  develop  a  new  head  where  the  tail  used  to  be; 
or  the  experimental  obliteration  of  the  polar  gradient  may 
cause  the  new  individual  to  develop  along  the  original 
lateral  symmetry  gradient,  with  a  head  on  one  side  and  a 
tail  on  the  other.  Just  as  slight  accidental  advantages  in 
oxygen  supply,  illumination,  or  other  conditions  which 
favor  growth  determine  the  location  of  the  animal  pole  of  the 
egg,  so  they  may  enable  some  group  of  cells  to  seize  control 
and  to  rearrange  an  adult  organism  along  new  axes  (Child,113 
pp.  158,  172). 

Although  there  is  still  considerable  doubt  as  to  the  exact 
mechanism  of  this  control,  more  and  more  evidence  is 
accumulating  to  show  the  importance  of  the  minute  electric 
currents  which  are  produced  in  these  metabolic  gradients. 
If  we  put  two  pieces  of  metal  of  different  composition 
into  a  solution  of  some  electrolyte  and  connect  them 
to  a  galvanometer,  we  find  a  current  flowing  between 
them.  If  the  electrodes  are  chemically  the  same 
but  the  concentration  of  the  electrolyte  about  them  varies, 
a  current  will  again  be  set  up.  In  the  tissue  there  are  no 
metal  electrodes  and  no  wires;  but  differences  in  ionic 
concentration  on  the  two  sides  of  cell  membranes  and 


48     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

differences  in  the  rates  of  oxidation  along  growing  axes 
give  rise  to  circuits  through  the  tissues  themselves  (Lillie267). 
If  two  regions  with  different  oxidative  rates  are  connected 
through  wires  to  a  galvanometer,  the  more  actively  growing 
or  more  motile  one  is  always  electro-negative  to  the  other; 
that  is,  the  current  flows  towards  it  in  the  wire.  In  the  tissue, 
of  course,  the  current  flows  from  .the  more  active  end  of  the 
metabolic  gradient  to  the  lower.  Similarly,  in  a  battery,  the 
zinc  plate  is  positive  to  the  copper,  although  the  copper 
terminal  is  positive  through  the  galvanometer  to  the  zinc 
terminal.  Years  ago  Hermann185  noticed  that  the  growing 
root  tips  of  seedlings  were  negative  to  other  parts  of  the  root. 
Miiller-Hettlingen337  confirmed  this  and  showed,  moreover, 
that  the  growing  tip  of  the  plant  was  negative  to  all  other 
regions.  Later,  in  1902,  Mathews301  found  that  the  head  of  a 
polyp  was  electro-negative  to  the  stem,  and  anterior  levels 
of  the  stem  negative  to  posterior  ones;  and  in  recent  years 
Child  and  his  students  have  found  gradients  of  electric 
potential  along  all  the  axiate  animals  and  plants  which 
they  have  studied  (Child113). 

We  are  just  beginning  to  see  that  these  minute  differences 
in  electric  potential  can  play  a  large  part  in  the  development 
and  life  of  the  organism.  They  not  only  bring  about  certain 
chemical  reactions  which  otherwise  would  not  take  place, 
but  they  direct  them  along  certain  lines.  One  of  the  simplest 
and  best  known  examples  of  the  "chemical  action  at  a  distance" 
is  found  in  the  electric  battery  where  two  pieces  of  zinc  and 
copper  form  the  electrodes  and  dilute  sulphuric  acid  serves 
as  the  electrolyte.  Very  little  chemical  action  takes  place  until 
the  two  pieces  of  metal  are  connected  by  a  wire,  but  immedi- 
ately after  that  the  zinc  begins  to  be  eaten  away.  Many  other 
interesting  examples  of  this  action  might  be  supplied,  and 
if  space  permitted  I  might  review  the  work  of  Lillie267 


THE  BASIS  OF  THE  RHYTHMIC  GRADIENT       49 


and  others  who  have  used  weak  electric  currents  to  build 
beautiful  structures  closely  resembling  corals,  seaweeds, 
trees,  toadstools,  etc.  Nineteen  years  ago  Mathews301  suggested 
that  we  might  be  able  to  modify  and  control  at  will  the 
regeneration  of  lost  parts  in  lower  animals  by  modifying 
the  bio-electric  currents,  and  recently  Lund282  and  Ingvar211 


Ilcum         Term. 


Jej. 


FIG.  8. — Shows  gradation  in  the  latent  period  of  the  dog's  small  intestine. 
The  ordinates  represent  parts  of  a  second;  the  abscissae,  distances  from  the 
pylorus.  The  data  shown  at  the  right  were  secured  from  distempered  or 
otherwise  diseased  dogs. 

have  shown  that  such  control  is  possible.  Lund  was  able  to 
determine  the  point  of  regeneration  in  Obelia;  and  Ingvar 
caused  the  cell  bundles  in  tissue  cultures  to  grow  along 
the  lines  of  force  produced  electrically  in  his  tissue  cultures. 
He  found,  moreover,  that  he  could  produce  these  effects 
•with  currents  comparable  in  intensity  with  those  found  in 
living  tissues. 

In  addition  to  the  axial  gradients  of  growth  there  are 


50    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

other  metabolic  gradients  in  various  organs.  As  was  to  be 
expected  from  the  character  of  the  electrical  phenomena, 
there  is  a  gradient  in  the  embryonic  heart  of  the  chick  from 
the  sinus  to  the  ventricle  (Child,113  p.  169).  MacArthur  and 
Jones288  found  a  gradation  in  respiratory  rate  in  the  nervous 
system  from  the  cerebrum  to  the  peripheral  nerves,  and 
Tashiro422  has  demonstrated  gradients  of  CO2  production 
along  nerves.  He  believes  that  these  gradients  which  are 
from  the  center  to  the  periphery  in  motor  roots  and  from 
the  periphery  to  the  center  in  sensory  roots  have  something 
to  do  with  the  conduction  of  impulses. 

This  long  digression  into  fields  distant  from  that  of  the 
intestine  has  been  made  in  order  to  show  the  growing  impor- 
tance of  the  gradient  idea  in  biology.  It  will  undoubtedly  be  a 
long  time  before  research  workers  are  in  agreement  as  to  the 
exact  significance  of  these  gradients,  but,  as  Child  says, 
there  can  be  no  doubt  as  to  their  existence.  They  are  there, 
and  the  natural  inference  is  that  they  must  be  useful  or  at 
least,  worth  studying. 


CHAPTER  VII 
OTHER  RELATED  GRADIENTS 

T  ATENT  PERIOD.  When  a  muscle  is  stimulated  it 
I  /ioes  not  respond  immediately.  There  is  a  short,  so- 
called  latent  period  the  length  of  which  depends 
largely  on  the  metabolic  rate  of  the  muscle.  As  the  metabolic 
rate  has  been  shown  to  vary  in  different  parts  of  the  gut,  we 
would  expect  the  latent  period  to  vary,  and  actually  it  can  be 
shown  that  it  does.  As  will  be  seen  in  the  next  chapter,  it  is 
quite  easy  to  show  a  gradient  of  latent  period  in  the  stomach. 
In  the  bowel  the  technical  difficulties  are  much  greater,  and 
it  is  almost  impossible  to  get  satisfactory  measurements 
with  some  animals.  In  many  others,  however,  I  have  been 
able  to  show  a  definite  gradation  from  a  short  latent  period 
in  the  lower  duodenum  or  upper  jejunum  to  a  long  one  in 
the  ileum.  Figure  8  shows  how  the  data  run  in  dogs.  The 
first  portion  of  the  duodenum  generally  reacted  poorly  and 
after  a  fairly  long  latent  period.  That  may  be  due  at  least 
in  part  to  its  relatively  greater  susceptibility  to  the  trauma 
of  excision  and  handling.  While  studying  these  latent  periods 
and  the  shapes  of  the  contraction  curves,  I  could  not  help 
being  greatly  impressed  with  the  marked  differences  which 
exist  between  the  muscle  in  different  parts  of  the  stomach, 
small  bowel  and  colon. 

TONE.  When  a  piece  of  duodenum  or  jejunum  is  cut  out 
it  tends  to  contract  down  to  perhaps  half  of  its  original 
length  and  the  ends  roll  over  so  as  to  form  little  cuffs. 

51 


52     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

A  piece  of  ileum  may  even  lengthen  a  little,  and  its  cuffs, 
if  any  form  at  all,  are  narrow  as  compared  with  those  of  the 
upper  bowel.  I  found  recently  that  these  little  cuffs  with 
their  differences  in  width  were  described  in  1902  by  a  medical 
student  (Wolff450) .  Similar  differences  in  the  tone  of  the  mus- 
cle from  different  parts  of  the  stomach  are  described  in  the 
next  chapter.  When  a  loop  of  bowel  is  full  of  food  and  actively 
segmenting  it  is  generally  contracted  tonically.  Later,  when 
it  empties,  it  may  relax  and  more  than  double  in  length 
(Alvarez,3  Mall,298  p.  451).  These  permanent  and  transitory 
differences  in  tone  are  undoubtedly  of  great  importance  in 
digestion,  and  should  be  studied  further.  As  Cannon84 
(p.  27),  also86  (p.  195),  and88  (p.  242),  and87  (p.  417),  has 
shown,  they  have  much  to  do  with  initiating  and  regulating 
peristalsis  in  all  parts  of  the  digestive  tract.  He  was  able  to 
reverse  the  direction  of  peristalsis  in  a  loop  of  intestine  by 
dipping  the  caudad  end  into  a  weak  solution  of  BaCI2 
(Cannon,90  p.  119).  As  is  well  known,  that  raises  the  tone  of 
the  muscle.  In  the  crop  of  the  sea  slug  (von  Brucke75)  and  in 
the  earthworm  (Biedermann,59  p.  483)  it  has  been  shown 
that  the  contractions  start  from  the  place  of  greatest  tension. 
Changing  that,  the  direction  of  peristalsis  can  be  reversed  at 
will.  Trendelenburg431  has  observed  the  tendency  of  a  loop  of 
guinea  pig  intestine  to  contract  more  at  the  cephalad  end 
than  at  the  caudad,  and  has  suggested  that  this  gradient 
of  tone  accounts  for  the  direction  of  peristalsis. 

RHYTHMIC  TENDENCY.  When  a  number  of  segments  from 
different  parts  of  the  rabbit's  intestine  are  placed  in  a 
beaker  of  warm  oxygenated  Locke's  solution,  the  duodenal 
segment  is  generally  the  first  to  begin  beating,  and  the  colon 
is  generally  the  last.  Figure  5  shows  also  that  when  a  number 
of  beating  segments  are  thrown  into  spasm  by  pilocarpin 


OTHER  RELATED  GRADIENTS  53 

and  then  released  again  by  atropin,  there  may  be  a  remarkable 
gradation  shown  in  the  tendency  to  resume  rhythmic  ac- 
tivity. Conditions  in  the  intestine  are  very  similar,  therefore, 
to  those  in  the  heart  where  the  excised  auricle  can  be  made 
to  beat  easily,  but  the  ventricle  only  with  difficulty.  If  this 
tendency  is  as  marked  in  the  intact  animal  as  it  is  in  the 
excised  segments,  its  usefulness  is  obvious.  It  will  conduce 
to  the  starting  up  of  normally  directed  peristalsis  after  the 
bowel  has  been  paralyzed  by  poisons  or  by  powerful  splanchnic 
inhibition. 

IRRITABILITY.  As  stated  in  the  preface,  the  first  gradient 
which  I  noticed  was  one  of  irritability.  I  found  that  the 
duodenum  was  more  responsive  to  distention  by  gases 
or  food  than  was  the  ileum.  Later,  while  working  on  men 
and  women  with  intestinal  fistulae  I  found  that  a  balloon 
in  the  jejunum  was  kneaded  and  pulled  on  almost  incessantly; 
in  the  ileum,  it  was  often  left  undisturbed  for  a  half  hour  or 
more,  and  in  the  colon  it  was  left  entirely  alone  except  for 
an  occasional  contraction  immediately  after  it  was  distended. 
A  search  through  the  literature  showed  that  others  have 
made  similar  observations.  Van  Braam  Houckgeest,194 
Floel,153  Schillbach386  (p.  281),  Bokai,61  Biedermann56  (pp. 
372  and  379),  Liideritz278  and,279  and  Bayliss  and  Starling,39 
all  comment  on  the  greater  activity  and  responsiveness  of 
the  duodenum  and  jejunum:  and  the  last  named  writers 
thought  that  "ascending  augmentor  stimuli"  and  the  "higher 
excitability  of  the  duodenal  end  of  the  gut"  might  perhaps 
have  something  to  do  with  the  preponderance  of  downward 
peristalsis.  Schillbach  used  faradic  stimuli  so  weak  that  they 
had  practically  no  effect  on  the  bowel  except  in  the  upper 
jejunum  and  upper  end  of  the  colon.  Similar  results 
were  obtained  by  Biedermann  with  the  galvanic  current. 


54     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

He  thought  the  irritability  was  graded  downwards  and  that 
there  must  be  a  histologic  gradient  perhaps  in  the  structure 
of  Auerbach's  plexus.  He  tried  to  prove  this  pharmacologically 
much  as  I  tried  in  1913. 

It  is  easy  to  show  the  gradient  of  irritability  in  the  bowel 
with  distending  balloons,  pinches,  and  salt  crystals,  but  it  is 
not  easy  to  show  it  with  the  electric  current.  I  have  tried 
many  times  to  work  out  a  satisfactory  technique  but  have 
never  been  able  to  convince  myself  that  the  threshold  for 
the  duodenum  is  less  than  that  for  the  ileum.  The  rhythmic 
changes  constantly  going  on  in  the  intestinal  muscle  and  the 
prolonged  refractory  periods  make  such  experiments  unsatis- 
factory and  inconclusive.  There  seems  little  doubt  that  the 
chemical  threshold  is  the  same  in  different  parts  of  the  gut; 
that  is,  five  segments  from  different  regions,  if  they  are  all 
beating  strongly,  will  respond  equally  to  minute  dosages  of 
drugs  like  barium  chloride  or  pilocarpin. 

Marked  differences  in  irritability  were  found  in  different 
parts  of  the  wall  of  the  stomach,  but  those  will  be  discussed 
in  the  next  chapter. 

EARLY  OBSERVATIONS  ON  THE  RHYTHMIC  GRADIENT. 
This  little  book  would  not  be  complete  without  references 
to  the  work  of  previous  writers  on  the  subject.  When  in  1913 
I  started  studying  the  differences  in  rhythmic  rate  which 
appeared  on  my  tracings  from  two  different  parts  of  the  bowel, 
Dr.  Walter  B.  Cannon  told  me  that  he  had  noticed  such  differ- 
ences but  he  had  never  had  time  to  analyze  them,  and  so  far 
as  he  could  remember,  he  had  never  read  anything  about 
them.  During  the  next  year  a  search  was  made  through  the 
literature,  and  little  was  found  that  would  lead  anyone  to 
suspect  that  the  neuromuscular  tube  of  the  small  intestine 
is  any  different  in  the  duodenum  from  what  it  is  in  the 


OTHER  RELATED  GRADIENTS  55 

ileum.  Even  Roith,375  who  had  the  vision  to  see  that  the 
peculiarities  of  colonic  activity  might  be  due  to  regional 
differences  in  muscle  and  tone,  states  that  the  small  intestine 
is  the  same  throughout.  After  long  search,  however,  I 
found  references  to  differences  in  rhythmicity  in  Luciani's 
"Textbook  of  Physiology,"276  and  in  articles  by  Legros  and 
Onimus,259  Liideritz,279  and  Laqueur.254  Legros  and  Onimus 
thought  that  the  emptiness  of  the  jejunum  was  probably 
due  to  its  fast  rate.  Nothnagel343  remarked  upon  the  fact 
that  in  the  rabbit  the  movements  of  the  upper  bowel  are 
stronger  and  more  continuous  than  those  of  the  lower. 
Stiles412  noticed  a  rhythmic  gradient  along  the  esophagus 
of  the  frog;  and  Bottazzi67  and68  (p.  341)  ascribed  the  aboral 
course  of  the  waves  in  the  esophagus  of  the  sea  slug  Aplysia 
to  the  greater  tone  and  excitability  of  the  oral  region  in 
which  they  arise.  He  suspected  a  difference  in  rate,  but  he 
could  not  show  it.  Bottazzi  deserves  much  credit  because  he 
knew  what  he  was  looking  for,  and  the  value  of  what  he 
found  in  the  esophagus.  I  cannot  tell  from  their  papers 
whether  the  later  writers  knew  of  the  work  of  Legros  and 
Onimus.  Pohl361  knew  of  Liideritz's  work,  and  Luciani  may 
have  derived  his  knowledge  from  the  same  source.  As  was 
shown  in  the  preceding  section,  a  number  of  the  older 
writers  observed  the  gradient  in  irritability.  Hess,187  and 
Brandl  and  Tappeiner72  noticed  the  gradient  in  pushing 
force  down  the  bowel,  described  in  Chapter  V. 

Unfortunately,  these  men  did  not  realize  the  value  of 
what  they  had  found;  they  did  not  have  the  present  day 
background  to  fit  it  into,  and  they  did  not  keep  hammering 
away  on  the  subject  until  they  compelled  their  confreres 
to  listen.  We  may  sometimes  regret  the  fact  that  textbooks 
are  sluggish  and  conservative  things,  but  when  we  remember 
that  it  often  takes  from  fifty  to  a  hundred  years  to  purge  them 


56     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

of  some  misquotation  or  false  conclusion,  we  should  perhaps 
be  glad  that  it  takes  ordinarily  from  ten  to  twenty  years  of 
reiteration  to  get  a  new  idea  included.  To  my  mind,  the 
main  cause  for  the  slow  development  of  our  knowledge  of 
the  mechanics  of  peristalsis  is  to  be  found  in  the  fact  that 
most  of  the  men  who  worked  on  the  bowel  were  so  con- 
cerned with  problems  of  nerve  supply  or  drug  action  that 
they  made  mention  of  important  physiological  observations 
only  in  passing.  A  striking  illustration  of  this. is  found  in 
Jacobj's212  description  of  reverse  peristalsis  in  the  colon. 
This  was  buried  away  and  lost  in  an  article  on  colchicum 
poisoning  until  some  time  after  Cannon's  independent 
discovery  of  the  same  phenomenon. 

ANATOMIC  DIFFERENCES.  The  differences  in  the  structure 
of  Auerbach's  plexus  in  different  parts  of  the  gut  have 
already  been  mentioned  (Gerlach164  and  Kuntz245).  The 
presence  of  "nodal  tissue"  at  the  cardia  and  ileocecal 
sphincter  will  be  discussed  in  Chapter  XI.  A  gradation  in 
the  thickness  of  the  muscular  coat  of  the  small  intestine 
from  the  duodenum  to  a  point  a  little  way  above  the  ileocecal 
sphincter  has  been  described  by  a  number  of  anatomists 
(Tourneux  and  Hermann,429  Flint,152  Merkel,319  Jonnesco,219 
KoIIiker,240  Monks323  and,324  Schafer384  (pp.  536  and  552); 
Todd427  (p.  145).  Unfortunately,  the  normal  transient 
differences  in  tone  and  the  uncertain  effects  of  the  fixing 
agents  make  it  hard  to  get  trustworthy  figures.  These  diffi- 
culties and  the  ways  of  meeting  them  are  discussed  in 
Rost's378  article  on  the  differences  in  the  thickness  and  tone 
of  the  muscular  wall  in  the  colon  of  man. 

One  of  the  most  interesting  graded  differences  is  the  one 
pointed  out  so  clearly  by  Monks.323'324  He  calls  attention 
to  the  fact  that  there  is  a  progressive  decrease  in  the  vascu- 


OTHER  RELATED  GRADIENTS  57 

larity  of  the  mesentery  from  the  duodenum  to  the  ileum. 
(See  also  Latarjet  and  Forgeot255).  Part  of  this  difference 
in  the  mesenterial  arches  is  due  to  the  greater  functional 
activity  of  the  mucous  membrane  in  the  jejunum,  but  part  of 
it  is  due  undoubtedly  to  the  greater  activity  of  the  muscle 
there.  These  observations  fit  in  with  those  of  Krogh,244 
who  has  shown  that  the  blood  supply  to  a  muscle  is  an 
accurate  index  of  its  metabolic  rate.  In  keeping  with  its 
sluggishness  and  its  slow  metabolic  rate,  the  colon  has  a 
relatively  poor  blood  supply;  so  poor  that  surgeons  have  to  be 
very  careful  when  making  anastomoses  not  to  impair  it 
further  (Okinczyc344). 


CHAPTER    VIII 
GRADED  DIFFERENCES  IN  THE  STOMACH  WALL 

WHEN  it  was  seen  that  the  rate  of  rhythmic  con- 
traction in  the  small  intestine  varies  inversely  as 
the  distance  from  the  pylorus,  the  next  question 
was:  How  about  the  other  parts  of  the  digestive  tract? 
Could  the  primitive  digestive  tube  have  been  constructed 
originally  so  that  the  rate  would  be  highest  at  the  pharynx 
and  lowest  at  the  anus?  Although  this  question  cannot  be 
answered  conclusively  as  yet,  there  is  considerable  evidence 
in  favor  of  the  view  that  the  whole  tract  once  showed  such  a 
gradation  (Alvarez5).  Thus,  the  rates  of  contraction  in 
different  parts  of  the  colon  of  the  rabbit  and  cat  fit  quite 
well  into  a  prolongation  of  the  curve  plotted  from  the  rates 
in  different  parts  of  the  small  bowel.  These  rates  vary  in  the 
rabbit  from  6  to  10  per  minute  near  the  cecum  to  from  3  to  5 
per  minute  near  the  anus. 

It  is  impossible  to  say  much  about  the  esophagus  in 
mammals  because  in  them  that  tube  is  made  up  almost 
entirely  of  striated  muscle;  and  the  smooth  fibers  appear 
only  in  the  lower  third  or  fourth.  Longitudinal  segments 
from  the  lower  end  of  the  esophagus  of  laboratory  animals 
show  a  high  rhythmicity  when  placed  in  oxygenated  Locke's 
solution.  The  fastest  rate  observed  in  the  cat  was  14  per 
minute  and  in  the  rabbit  19  per  minute.  As  we  should 
expect  if  my  hypothesis  is  correct,  these  rates  are  higher 
than  those  for  the  excised  duodenal  segments  in  these 
animals.  In  the  frog's  esophagus,  where  the  muscle  is  all  of 

58 


DIFFERENCES  IN  THE  STOMACH  WALL          59 

the  smooth  variety,  we  can  see  that  the  rate  of  rhythmic 
contraction  varies  inversely  as  the  distance  from  the  phar- 
ynx. I  have  shown  these  differences  also  in  the  esophagus  of  a 
snake.  In  the  frog  the  esophageal  rate  was  generally  faster 
than  that  of  any  other  part  of  the  digestive  tract. 

Even  if  further  work  on  animals  should  show  definitely 
a  gradation  of  rhythmic  activity  from  pharynx  to  anus,  we 
should  still  have  to  explain  the  low  rate  of  the  gastric  waves 
in  mammals : — from  3  to  4  per  minute  in  the  rabbit,  dog  and 
man,  and  from  4  to  6  per  minute  in  the  cat.  A  possible  way 
out  of  this  difficulty  is  suggested  by  the  literature  on  another 
muscular  tube — the  heart.  Gaskell159  looked  on  that  organ 
as  an  elaboration  of  a  simple  tube  which  has  become  twisted 
on  itself  and  has  bulged  in  places.  There  the  muscle  has 
become  specialized  so  that  it  can  contract  and  empty  its 
cavities  more  quickly.  Gaskell  felt  that  the  "development  of 
this  nearer  approach  to  striated  muscle  is  made  at  the 
expense  of  the  original  rhythmical  power." 

THE  PRIMITIVE  DIGESTIVE  TUBE  AND  ITS  MODIFICATIONS. 
A  glance  at  Figure  9  will  show  how  the  stomach  also  has  been 
evolved  from  a  simple  tube,  first  by  an  enlargement;  secondly, 
by  a  bending  of  the  pylorus  towards  the  cardia;  and  thirdly, 
by  the  addition  of  one  or  more  cecal  pouches.  The  stomach  of 
the  eel  consists  almost  entirely  of  such  a  pouch  which  has 
grown  from  the  convex  side  of  a  bend  in  the  original  tube. 
It  is  very  obvious  in  such  a  stomach  that  the  primitive  tube 
is  to  be  found  along  the  lesser  curvature.  Even  the  com- 
plicated stomachs  of  ruminants  can  be  resolved  into  a  series 
of  ceca  arranged  along  the  original  tube  (Oppel,346  Hunting- 
ton196).  The  fundus  of  the  human  stomach  represents  such  a 
cecum  which  very  early  in  life  grows  out  from  the  greater 
curvature  (Keith  and  Jones,232  Lewis,262  p.  500).  Lewis  shows 


60    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

that  in  a  10  mm.  human  embryo,  the  stomach  is  made  up  of 
three  parts:  The  expanded,  conical  lower  end  of  the  eso- 
phagus; the  long  tubular  antrum,  a  little  wider  than  the 
adjacent  duodenum;  and  a  small  fundus.  The  end  of  the 
esophagus  meets  the  pyloric  antrum  at  the  incisura  angularis. 


FIG.  9. — Shows  the  development  of  the  stomach,  (a)  Stomach  of  the 
pickerel  (Nuhn);  (6)  stomach  of  Proteus  anguineus  (Nuhn);  (c)  stomach  of 
Scincus  ocellatus  (Nuhn) ;  (d)  stomach  of  the  eel  (Huntington) ;  (e)  scheme  of 
the  ruminant  compound  stomach  (Nuhn);  (/)  stomach  of  a  10  mm.  human 
embryo  (Lewis). 


Later  the  fundus  grows  at  the  expense  of  the  other  two  parts 
so  that  in  the  adult  the  end  of  the  esophagus  is  represented 
only  by  the  cardiac  antrum  and  that  prolongation  along  the 
lesser  curvature  which  forms  the  gastric  canal.  Thus  in  the 
adult,  the  pyloric  antrum  makes  up  a  much  smaller  part 
of  the  stomach  than  it  did  originally  (Fig.  9  F). 


DIFFERENCES  IN  THE  STOMACH  WALL          61 

The  primitive  tube  must  accordingly  be  looked  for  along 
the  lesser  curvature.  It  is  suggestive  that  this  part  of  the 
stomach  is  lined  by  an  epithelium  differentiated  least  of  all 
from  that  of  the  intestine;  that  is,  the  glands  are  mainly  of 
the  pyloric  type  (Bensley,47  Lansdown  and  Williamson252). 
A  similar  arrangement  is  found  in  most  of  the  domestic 


FIG.  10. — A  diagram  of  the  cat's  stomach  to  show  the  location  of  the 
principal  strips  studied  and  the  types  of  tracing  peculiar  to  the  different 
regions.  The  time  tracing  represents  thirty-second  intervals. 

animals  (Haane175).  It  is  interesting  also  that  many  animals, 
including  man,  have  a  loop  of  muscle  fibers  along  the  lesser 
curvature  which  on  contracting  make  a  gutter,  or  in  the 
ruminants  and  kangaroos  an  actual  tube  which  conducts 
fluids  from  the  cardia  to  the  pylorus.  In  this  way  the 
primitive  tube  is  largely  restored;  and  food  is  prevented 
from  entering  the  cecal  parts  of  the  stomach.  This  tube  is 
called  the  canalis  gastricus  (Jefferson214). 

If  this  idea  of  a  pouch  evolved  from  a  primitive  tube  is 
correct,  we  should  expect  to  find  the  most  rhythmic  tissue 
on  the  lesser  curvature  near  the  cardia.  Actually,  we  do 
find  it  there  (Alvarez5). 


62     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 


DIFFERENCES  IN  RHYTHMICITY.  Differences  in  rhythmicity 
were  shown  by  cutting  off  little  strips  of  muscle  from  differ- 
ent parts  of  the  stomach  and  getting  them  to  contract  in 
warm  aerated  Locke's  solution.  The  segment  from  the  lesser 


Cardia,  L.  Curv. 


JPreantrum,  L.  Curv. 


Antrum 


MicCale,  Or.  Curv. 


Gr,  Curv. 


Cardia 


Preantrum 


Cardia 


Antrum 


FIG.  ii. — Records  from  five  strips  from  different  parts  of  the  dog's  stomach; 
of  three  strips  from  the  lesser  curvature  of  the  human  stomach  and  from  four 
strips  from  the  greater  curvature  of  the  human  stomach. 

curvature  next  the  cardia  always  showed  the  greatest 
tendency  to  rhythmic  contraction.  Strips  from  the  greater 
curvature,  and  particularly  from  the  pyloric  antrum,  were 
slow  in  starting;  and  many  would  not  contract  at  all. 
The  rate  varied  ordinarily  from  about  11  at  the  cardia  to 


DIFFERENCES  IN  THE  STOMACH  WALL          63 

about  2  near  the  pylorus.  In  the  rabbit,  for  some  unknown 
reason,  the  muscle  on  the  greater  curvature  next  to  the 
pyloric  antrum  sometimes  showed  a  tendency  to  beat 
almost  as  fast  as  that  from  near  the  cardia.  Figure  10  shows 
that  there  is  somewhat  of  a  rhythmic  gradient  from  the 
cardia  to  the  pylorus.  It  shows  also  the  marked  differences  in 
the  shapes  and  amplitudes  of  the  contractions  in  the  different 
regions.  On  the  lesser  curvature  the  amplitude  is  very  small, 
and  in  the  antrum  it  is  large.  Figure  1 1  shows  that  these 
differences  are  just  as  characteristic  in  tracings  from  bits 
of  muscle  removed  from  the  human  stomach.  The  peculiar 
form  of  the  contraction  curve  exhibited  by  the  muscle  in  the 
pyloric  antrum  was  observed  even  in  the  frog. 

DIFFERENCES  IN  TONE.  Differences  in  tone  were  observed 
while  studying  the  strips  of  excised  muscle.  When  the  pieces 
were  removed  on  the  lesser  curvature,  not  only  did  they 
contract  markedly,  but  the  edges  of  the  cut  retracted  so  that 
the  piece  was  several  sizes  smaller  than  the  hole.  On  the 
greater  curvature,  the  piece  sometimes  stretched  a  little 
and  became  even  larger  than  the  hole.  The  differences  in  the 
amplitude  of  contraction  in  the  different  segments  may  be 
ascribed  partly  to  these  differences  in  tone  and  partly  to 
differences  in  the  structure  and  arrangement  of  the  muscle 
fibers. 


DIFFERENCE  IN  IRRITABILITY  AND  LATENT  PERIOD.  A 
search  of  the  literature  showed  that  several  men  have 
observed  local  differences  in  the  irritability  of  the  gastric 
wall.  Meltzer,317  noted  that  the  fundus  was  rather  unrespon- 
sive and  that  the  whole  stomach  was  less  sensitive  than  the 
bowel.  Liideritz,280  noted  that  the  contraction  often  appeared 


64     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

cardially  to  the  stimulated  place.  He  thought  that  the  lesser 
curvature  was  more  sensitive  than  any  other  place.  He  noted 
the  peculiar  type  of  reaction  in  the  pyloric  antrum,  and  the 
insensitiveness  of  the  fundus.  Ducceschi,131  studied  the 
irritability  of  the  interior  of  the  stomach.  He  thought  the 
reactions  to  mechanical  stimuli  were  quicker  and  more 
energetic  near  the  pylorus  than  anywhere  else.  The  cardia, 


FIG.  12. — Anterior  surface  of  the  stomach  of  the  cat,  showing  the  average 
intent  periods  after  faradic  and  galvanic  stimulation  in  different  regions. 
The  figures  indicate  seconds.  AB  is  the  dividing  line  between  the  pars 
pylorica  and  the  body  of  the  stomach.  The  other  unbroken  line  represents 
the  pylorus. 

however,  was  most  responsive  to  faradic  stimulation,  and  its 
latent  period  was  shortest.  Weak  acids  also  had  a  more 
pronounced  stimulating  effect  on  the  cardia  than  on  the 
fundus.  In  the  pyloric  antrum,  the  effect  was  generally 
reversed,  the  active  movements  being  inhibited.  The  presence 
of  a  balloon  in  the  antrum  almost  always  gave  rise  to  active 
peristalsis;  but  this  was  not  the  case  in  the  fundus.  Water- 
ston,440  comments  on  the  local  differences  in  the  response  of 
the  human  stomach  to  the  formalin  in  embalming  fluid. 


DIFFERENCES  IN  THE  STOMACH  WALL          65 

He  thinks  the  pyloric  sphincter  and  the  upper  end  of  the 
pyloric  antrum  have  the  most  irritable  muscle.  Carlson,95 
has  noted  that  the  hunger  contractions  are  mainly  in  the 
fundus  while  the  digestive  contractions  are  mainly  in  the 
pyloric  part.  "  Either  these  two  regions  of  the  stomach  react 
differently  to  local  stimulation  of  the  gastric  mucosa  or 
else  the  nervous  mechanisms  concerned  .  .  .  are 
different."  May,302  found  the  inhibitory  effect  of  vagus 
stimulation  more  pronounced  on  the  cardia  than  on  the 
pyloric  end  of  the  stomach. 

Barbera's  work  is  very  important.30  He  found  that  when 
the  stomach  of  a  frog  is  stimulated  at  any  point  by 
weak  faradic  shocks,  the  contraction  appears  first  at  the 
cardia.  He  found  that  this  is  due  to  a  shorter  latent 
period  at  the  cardia,  i.e.,  8.4  seconds,  as  compared  with 
10.2  seconds  in  the  middle  region,  and  13.5  seconds  near 
the  pylorus.  I  confirmed  this  work  of  Barbera  (Alvarez6), 
and  showed  also  that  the  cardia  is  the  most  irritable  part 
of  the  frog's  stomach.  Frequently  stimulation  of  the  pyloric 
region  brought  about  contractions  near  the  cardia  and  in 
the  duodenum  before  any  effect  was  observed  under  the 
electrodes. 

Similar  work  was  done  on  the  stomachs,  excised  and 
intact,  of  rabbits,  cats  and  dogs.  The  more  satisfactory  work 
was  done  on  the  excised  stomachs  because  the  irritability 
of  the  stomach  in  the  intact  animal,  anesthetized,  and  with 
the  abdomen  open,  is  considerably  lower  than  that  of  the 
organ  removed  from  the  body  and  kept  warm  in  a  moist 
chamber. 

In  the  rabbit,  the  reaction  to  electrical  stimulation  near 
the  cardia  is  almost  immediate.  This  is  due  largely  to  the 
fact  that  strands  of  striated  muscle  extend  from  the  eso- 
phagus onto  the  stomach  and  2  cm.  beyond  the  cardiac 


66     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

thickening.  Figure  12  shows  that  the  latent  period  lengthens 
as  we  pass  from  the  cardia  to  the  pylorus  and  from  the 
lesser  to  the  greater  curvature. 

The  pyloric  ring  was  more  irritable,  and  showed  a  shorter 
latent  period  than  did  the  rest  of  the  antrum.  This  point 
should  be  emphasized,  as  it  may  have  important  clinical 
bearings.  The  duodenum,  a  few  millimeters  away  from  the 
antrum,  responded  much  more  promptly  to  the  galvanic 
current.  For  some  unknown  reason,  the  difference  was  not 
so  marked  with  the  faradic  current.  There  is  a  definite 
gradation  in  the  ratio  between  the  latent  periods  with  the 
two  types  of  current  in  different  parts  of  the  stomach;  but 
the  exact  explanation  for  it  will  have  to  await  further 
study. 

Some  work  was  done  on  human  stomachs  excised  shortly 
after  death,  and  in  situ  during  abdominal  operations,  but  the 
results  were  not  very  satisfactory.  Enough  was  done  to  show 
the  differences  between  the  effects  of  faradic  and  galvanic 
stimulation  in  the  antrum,  and  the  differences  in  irritability 
between  the  stomach  and  duodenum. 

Much  of  the  sluggishness  of  the  intact  stomach  seems  to 
be  due  to  nervous  inhibition.  If  the  irritability  of  the  muscle 
were  dependent  upon  its  nervous  connections,  we  should 
expect  the  reactions  to  become  progressively  slower  after 
removal  of  the  stomach  from  the  animal,  and  particularly 
after  the  trauma  of  cutting  the  strips.  Yet  the  opposite  is 
true.  The  latent  period  was  often  shorter,  and  the  rhythmic- 
ity  in  all  but  the  cardiac  strip  was  generally  much  better  on 
the  second  or  third  day  than  on  the  first.  Good  records  were 
secured  from  bits  of  muscle  removed  from  the  stomach  of  an 
executed  criminal  and  kept  in  Locke's  solution  at  io°C.  for 
four  days. 


DIFFERENCES  IN  THE  STOMACH  WALL          67 

DIFFERENCES  IN  EXCISED  SEGMENTS.  There  was  a 
marked  difference  in  the  appearance  of  the  contraction 
curve  obtained  by  stimulating  bits  of  muscle  cut  from 
the  pyloric  antrum  and  the  cardiac  region  of  the  frog. 
The  cardiac  strips  showed  by  far  the  greater  rhythmicity 
(Alvarez,7).  They  suffered  more  from  the  trauma  of  excision 


FIG.  13. — Contraction  curves  from  strips  from  the  frog's  antrum  (upper) 
and  the  cardia  (lower).  The  same  strength  of  faradic  current  was  used. 
Time  markings  represent  seconds.  Magnification  oflever  4.5  :  21. 


and  they  recovered  slowly  as  compared  with  the  antral 
strips.  They  suffered  more  damage  also  from  strong  faradic 
currents.  They  did  not  stand  being  kept  in  the  ice-box  so 
well  as  did  the  strips  from  the  antrum.  Strips  from  the 
middle  of  the  frog's  stomach  reacted  more  like  those  from 
the  cardia  than  like  those  from  the  antrum.  The  muscle  in 
the  antrum  of  the  frog's  stomach  is  firmer  to  the  touch  and 
there  is  a  marked  difference  between  it  and  that  in  the  rest  of 
the  stomach. 


68    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

Similar  differences  were  found  in  the  reactions  to  artificial 
stimulation  of  strips  of  muscle  excised  from  different  regions 
of  the  stomachs  of  cats,  dogs,  and  rabbits  (Alvarez8).  Speak- 
ing roughly,  the  latent  period  varied  inversely  as  the  distance 
from  the  cardia.  The  shape  of  the  contraction  curve  was 
different  and  characteristic  for  the  various  regions  of  the 
stomach.  (Fig.  13.)  The  muscle  from  the  fundus  showed  a 
great  tendency  to  remain  tonically  contracted  after  stimu- 
lation, while  the  antral  muscle  relaxed  promptly.  The 
muscle  in  the  pyloric  antrum  seems  to  be  particularly  fitted 
to  carry  on  the  active  work  of  the  stomach,  while  the  fundus 
serves  to  maintain  a  steady  tonic  pressure  on  the  contents. 
The  muscle  from  the  antrum  has  a  color  different  from  that 
in  the  rest  of  the  stomach.  It  is  redder  and  tough  like  that  of 
a  gizzard.  The  muscle  from  the  pacemaking  region  is  soft 
to  the  touch  like  coagulated  fibrin.  Todd,427  (p.  95)  says  the 
muscular  fibers  in  the  pyloric  region  are  bulkier  and  more 
separated  from  each  other  than  in  the  cardiac  portion  of  the 
stomach. 

When  the  strips  were  left  for  forty-eight  hours  in  the 
ice-box  those  from  the  antrum  showed  themselves  peculiar 
in  that  their  latent  periods  were  shortened  while  those  of 
the  other  strips  were  more  or  less  lengthened.  In  diseased 
animals  all  but  one  or  two  strips  generally  showed  a  lessened 
irritability  and  a  lengthened  latent  period.  In  some  of  these 
sick  animals  the  latent  period  of  the  antral  strip  was  defi- 
nitely shortened.  This  lengthening  of  the  latent  period  at 
the  cardia  with  a  shortening  at  the  pylorus  often  upset  the 
normal  gradient  usually  found. 

DIFFERENCE  IN  CATALASE  CONTENT.  I  have  already 
commented  on  the  gradation  in  the  catalase  content  of  the 
muscle  from  the  duodenum  to  the  ileum.  A  similar  gradation 


DIFFERENCES  IN  THE  STOMACH  WALL 


69 


was  found  in  the  stomach  (Alvarez  and  Starkweather14). 
This  gradient  was  more  marked  along  the  lesser  curvature 
than  on  the  greater.  In  the  rabbit  the  amount  of  catalase 
was  larger  along  the  lesser  curvature  than  along  the  greater. 
For  some  unknown  reason  this  ratio  was  reversed  in  the 


FIG.  14. — Shows  the  superimposed  outlines  of  a  number  of  gastric  radio- 
graphs taken  cinematographically.  Note  the  small  amplitude  of  contraction 
in  the  upper  part  of  the  stomach  and  the  change  in  the  character  of  the  waves 
when  they  reach  the  pyloric  antrum.  (From  Groedel.) 

cat  and  dog.  Further  work  needs  to  be  done  on  the  metabol- 
ism of  the  muscle  in  the  stomach  wall. 

DISCUSSION 

It  has  been  well  established  by  many  workers  that  the 
stomach  performs  its  functions  after  section  of  the  extrinsic 
nerves  (Cannon,81  p.  429;  Rubaschow,379  Krehl,241  and  evert 
after  its  removal  from  the  body  (Hofmeister  and  Schiitz191). 
We  see  now  that  local  peculiarities  in  the  muscle,  with 


70     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

graded  differences  in  rhythmicity,  irritability,  tone  and 
latent  period  probably  have  most  to  do  with  directing  the 
peristaltic  wave  as  it  travels  over  the  stomach.  As  in  the 
heart,  so  here,  the  waves  probably  have  their  origin  in 
the  most  highly  rhythmic  and  sensitive  area.  We  may  say 
perhaps  that  the  region  on  the  lesser  curvature  next  to  the 
cardia  is  the  pacemaker  for  the  stomach.  It  must  be  remem- 
bered, however,  that  the  activities  of  the  heart  and  stomach 
are  very  different.  In  one,  the  impulse  travels  so  rapidly 
that  the  organ  appears  to  contract  as  a  unit;  in  the  other  a 
series  of  waves  travel  slowly  over  the  sac,  gently  kneading  its 
contents. 

A  glance  at  one  of  Groeders  illustrations  (Fig.  14)  made  up 
of  the  superimposed  outlines  of  a  dozen  serial  radiographs 
of  the  same  human  stomach,  will  show  how  little  the  lesser 
curvature,  as  far  as  the  incisura  angularis,  is  affected  by 
the  peristaltic  waves.  The  amplitude  is  very  small,  just  as 
it  is  in  excised  segments  of  muscle  from  this  region.  Appear- 
ing at  a  variable  distance  from  the  fundus,  the  gastric  waves 
seem  to  travel  almost  entirely  along  the  greater  curvature, 
getting  deeper  as  they  approach  the  antrum.  At  that  point 
their  character  suddenly  changes :  they  involve  the  whole 
circumference  of  the  stomach  and  are  so  deep  that  they 
sometimes  meet  in  the  center.  It  seems  to  me  that  these 
local  differences  in  the  shape  and  depth  of  the  peristaltic 
wave  correspond  perfectly  to  the  regional  peculiarities 
of  the  tone  and  amplitude  of  contraction  of  the  muscle  fibers 
through  which  it  must  pass.  The  reader  may  grasp  the  idea 
more  easily  if  he  will  think  of  an  impulse  traveling  down  a 
series  of  strings,  the  tension  of  which  varies  inversely  as 
the  distance  from  the  top.  At  the  upper  end  the  waves  will 
have  a  low  amplitude  and  a  high  frequency,  while  at  the 
lower  they  will  have  a  large  amplitude  and  a  low  frequency. 


DIFFERENCES  IN  THE  STOMACH  WALL          71 

It  is  interesting  in  this  connection  that  Jenkins  and  Carl- 
son,215 say,  after  studying  the  muscles  of  a  number  of 
molluscs  that  "the  rates  of  nervous  impulse  and  forms  of  the 
myograms  of  the  three  well  express  the  differences  in  the 
degree  of  activity  manifested  by  the  three."  The  squid  is 
the  most  active  simply  because  it  has  the  most  efficient 
muscles. 

In  the  heart,  when  the  sinus  node  is  damaged,  the  tissue 
with  the  next  highest  rate  assumes  the  pace.  Dittler,129 
noticed  a  similar  shifting  in  the  crop  of  the  sea  slug  Aplysia; 
and  we  know  that  waves  will  run  aborally  over  the  pyloric 
portion  of  the  dog's  stomach  even  after  it  has  been  separated 
from  the  cardiac  end  (Kirschner  and  Mangold236).  There 
is  little  interference  with  peristalsis  in  the  human  stomach 
after  so-called  sleeve  resections  of  the  middle  portion  (Faulha- 
ber  and  von  Redwitz148);  and  Cannon  has  shown  that 
waves  will  keep  traveling  over  the  organ  quite  normally 
after  the  healing  of  several  encircling  cuts  which  have 
been  made  through  the  muscle  down  to  the  mucosa  (Can- 
non,89 p.  258). 

Rather  against  the  view  that  the  waves  originate  near 
the  cardia  is  the  common  observation  that  they  seem  to 
appear  now  here,  now  there  on  the  greater  curvature. 
Cannon89  (p.  257)  felt  that  the  pulsatile  source  of  the 
gastric  wave  has  no  fixed  seat.  He  showed  that  a  wave  is 
likely  to  appear  at  the  spot  where  a  certain  balance  is  struck 
between  the  tone  of  the  muscle  and  the  internal  tension. 
My  records  from  the  intact  intestine  show  clearly  that 
a  peristaltic  rush  which  apparently  has  begun  in  the 
lower  ileum  has  really  come  as  an  unnoticed  ripple  all 
the  way  from  the  duodenum  (Alvarez,3  p.  273,  Fig.  3).  I 
believe  that  the  same  thing  takes  place  in  the  stomach;  that  is, 
ripples  sent  out  from  the  cardia  deepen  into  large  waves  at 


72     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

certain  points  where  the  conditions  of  tension  are  suitable. 
Carefully  made  serial  plates  will  show  these  ripples  along  the 
lesser  curvature  as  far  up  as  the  cardia.  Work  now  being 
done  in  my  laboratory  shows,  moreover,  that  strong  action 
currents  run  rhythmically  even  over  stomachs  which  show 
absolutely  no  sign  of  peristalsis. 

One  question  which  may  arise  is:  Why  should  the  rates  of 
the  excised  strips  in  the  rabbit  and  dog  be  so  much  higher 
than  that  of  the  intact  stomach?  Only  in  the  cat  do  they 
correspond  at  all.  It  is  different  in  the  intestine  where  the 
rates  of  the  intact  bowel  and  of  the  excised  segments  agree 
quite  closely.  The  faster  rates  in  the  stomach  probably 
indicate  a  reserve  rhythmicity  of  which  the  cardia  has  the 
greatest  amount.  It  does  not  seem  likely  that  the  normal 
slow  rate  is  due  to  depressor  effects  from  the  vagus,  as 
peristalsis  is  not  quickened  after  double  vagotomy  (Cannon,81 
p.  432).  More  probably  the  longer  intervals  between  beats 
are  needed  for  adequate  rest  and  recovery  so  that  the  muscle 
can  maintain  a  constant  level  of  efficiency.  For  the  same 
reason  the  medusae  pulsate  normally  at  only  about  one- 
seventh  of  the  rate  that  they  are  capable  of  maintaining 
under  certain  conditions  (Mayer,303  p.  379). 

Clinical  Applications.  If  these  gradients  of  rhythmicity 
irritability,  latent  period,  tone,  and  (probably)  metabolism, 
are  helpful  in  maintaining  the  normal  aboral  peristalsis, 
it  is  very  likely  that  an  upset  in  them  will  interfere  with 
the  motility  of  the  stomach.  We  have  seen  that  the  muscle 
at  the  cardiac  end  is  so  much  more  sensitive  to  adverse 
conditions  and  to  toxins  that  the  gradients  are  found 
flattened  in  diseased  animals.  The  gradients  may  be  upset  also 
by  ulcers  near  the  pylorus  which  greatly  increase  the  irritabil- 
ity of  that  region;  and  actually,  at  times,  we  do  see  reverse 
peristalsis  in  the  stomach. 


DIFFERENCES  IN  THE  STOMACH  WALL          73 

The  theory  that  the  gastric  waves  originate  near  the 
cardia  is  helpful  in  explaining  some  of  the  peculiarities  of 
gastric  motility  with  ulcers,  particularly  on  the  lesser  curvature. 
Ordinarily  a  wave  originating  at  the  cardia  has  to  travel  a 
little  faster  along  the  greater  curvature  than  along  the  shorter 
lesser  curvature  if  the  two  ends  are  to  reach  the  pylorus 
at  the  same  time.  Not  infrequently  a  small  ulcer  on  the 
lesser  curvature  calls  attention  to  itself  by  altering  the 
rate  of  conduction  so  that  the  two  ends  of  the  wave  do  not 
reach  the  pylorus  simultaneously.  The  resulting  distortion  in 
that  region  is  easily  recognized  by  the  expert.  Often  in  these 
cases  the  stomach  does  not  empty  on  time,  although  it  can 
easily  be  seen  that  the  pylorus  is  patulous.  Sometimes  the 
arrival  of  part  of  the  wave  at  the  pylorus  seems  to  block 
the  other  part  of  it  still  advancing  along  the  other  curvature. 
It  seems  to  me  probable  that  such  differences  in  conduction 
would  be  still  more  exaggerated  after  operations  which 
shorten  the  lesser  curvature.  A  number  of  surgeons  have 
actually  found  that  a  V-shaped  excision  for  ulcer  on  the 
lesser  curvature  must  not  be  done,  because  it  leaves  a 
stomach  that  does  not  empty  properly  (Mayo,305  Stewart 
and  Barber410).  If  any  tissue  is  to  be  removed  from  one  curv- 
ature, a  similar  amount  must  be  removed  from  the  other, 
and  the  so-called  sleeve  resection  leaves  a  stomach  which 
functions  quite  normally.  Theoretically  the  sleeve  should 
be  a  little  wider  on  the  greater  curvature  than  on  the 
lesser. 

While  watching  gastric  peristalsis  in  the  rabbit  and  also 
in  man  it  has  often  seemed  to  me  that  there  must  be  a  wave 
of  excitation  traveling  ahead  of  the  visible  contraction. 
Owing  to  its  greater  irritability  and  shorter  latent  period,  the 
pyloric  ring  can  respond  to  this  excitation  a  little  ahead  of 
time,  and  in  doing  so,  it  blocks  the  advancing  peristaltic 


74     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

wave  and  keeps  that  from  putting  any  pressure  on  the 
sphincter.  Time  and  again  in  cats  I  have  watched  a  similar 
mechanism  protecting  the  ileocecal  ring  against  undue 
pressure  from  the  colonic  side.  It  contracts  firmly  in  the  face 
of  the  advancing  colonic  waves  (reverse  peristalsis)  and 
blocks  them  before  they  can  force  material  past  the  sphinc- 
ter. Similarly,  the  sacculus  rotundus  in  the  rabbit  protects 
the  ileocecal  sphincter  from  too  much  force  from  above.  It 
has  been  shown  in  some  of  the  lower  forms  of  life  that  intes- 
tinal material  does  not  press  up  to,  and  pack  against  the 
sphincters.  The  real  barrier  is  not  the  valve  but  a  ring  of 
muscle  with  high  tone  and  rhythmicity  placed  around  or 
just  above  it  (Bottazzi67  von  Briicke74).  This  not  only 
blocks  approaching  waves  but  starts  up  reverse  ones,  which 
save  the  sphincter  from  being  put  under  pressure.  These 
observations  must  be  thought  of  when  we  find  a  large 
six-hour  residue  in  the  stomach,  good  peristalsis  and  an  open 
pylorus. 

It  is  well  known  that  the  pyloric  sphincter  sometimes 
shows  considerable  spasm  even  when  the  lesion  causing  this 
spasm  is  well  up  on  the  stomach  or  down  in  the  bowel. 
This  might  be  explained  as  being  due  to  the  greater  irritabil- 
ity of  the  sphincter  as  compared  with  the  surrounding 
muscle.  Having  a  lower  threshold  it  can  pick  up  and  respond 
to  stimuli  which  are  ineffective  elsewhere. 

Similarly,  when  the  presence  of  an  ulcerated  duodenum  or 
an  inflamed  gall-bladder  in  the  upper  part  of  the  abdo- 
men makes  the  whole  stomach  extremely  irritable,  we  occa- 
sionally see  hourglass  contractions.  In  these  cases  it  may 
be  that  a  histological  study  would  show  little  erosions  of 
the  gastric  mucous  membrane  or  other  sources  of  local  irri- 
tation which  ordinarily  would  be  insufficient  to  bring  about 
such  contractions. 


DIFFERENCES  IN  THE  STOMACH  WALL          75 

The  presence  of  the  gradient  helps  to  explain  the  per- 
sistence with  which  the  muscle  in  the  lower  part  of  the 
stomach  tends  to  force  the  food  through  the  pylorus  instead 
of  through  the  stoma  of  a  gastro-enterostomy.  An  ideal  result 
might  be  obtained  if,  at  the  time  of  operation,  we  could  only 
reverse  the  pyloric  segment  of  the  stomach  so  that  the 
peristaltic  waves  would  tend  to  run  in  the  direction  of  the 
stoma  and  not  towards  the  pylorus. 


CHAPTER  IX 

PRACTICAL  APPLICATIONS  OF  THE 
GRADIENT   IDEA 


IF  the  downward  gradient  is  of  value  to  us  in  health,  it 
follows  as  a  corollary  that  upsets  in  the  gradient  should 
produce  symptoms  of  disease.  As  will  be  seen  later,  such 
upsets  have  been  observed  repeatedly  in  animals,  and  it  is 
highly  suggestive  that  most  of  these  animals  were  sickly; 
some  of  them  were  refusing  food,  and  others  were  even 
vomiting.  The  main  question  before  us  then  is:  Are  these 
upsets  present  ordinarily  with  the  digestive  troubles  of  man, 
and  if  so,  are  they  responsible  for  the  disturbances  in  motil- 
ity  then  observed?  Unfortunately,  these  questions  cannot 
yet  be  answered  with  certainty.  Other  factors  may  easily 
be  more  important  in  some  cases.  Thus  a  general  increase 
in  the  irritability  of  the  bowel  might  have  more  to  do  with 
the  production  of  a  diarrhea  than  a  steepening  of  the  gradi- 
ent, and  other  factors  about  which  we  know  little  may  be  at 
work.  On  account  of  these  gaps  in  our  knowledge  much  of 
what  follows  must  of  necessity  be  purely  theoretical  or 
based  on  analogy.  It  seems  to  me,  however,  that  so  long  as 
the  reader  will  keep  separate  in  his  mind  that  which  has 
been  proved  and  that  which  is  merely  suggestive,  it  can  do 
no  harm  to  set  forth  in  a  logical  manner  the  various  ways 
in  which  the  gradient  may  theoretically  be  upset,  and  the 
ways  in  which  such  upsets  may  affect  the  motility  of  the 
tract.  After  that  has  been  done,  it  will  be  easier  to  analyze 
the  disturbances  actually  observed  with  various  lesions, 

76 


APPLICATION  OF  THE  GRADIENT  IDEA  77 

and  to  see  whether  or  not  they  agree  with  those  to  be  expect- 
ed according  to  the  theory.  It  is  most  encouraging  to  find 
that  they  do  agree  remarkably  well  in  many  cases;  so  well 
that  we  now  have  an  easy  explanation  for  many  of  the 
observations  that  have  long  puzzled  the  gastro-enterologist, 
the  roentgenologist,  and  the  surgeon. 

In  many  places  during  the  following  discussion  I  may  use 
the  word  gradient,  although  the  plural,  gradients,  may  be  a 
more  appropriate  term.  Perhaps  it  is  a  distinction  without  a 
difference,  because  the  several  gradients  are  probably  all 
related  and  interdependent.  As  I  have  stated  before,  my 
impression  is  that  the  metabolic  gradient  is  the  underlying 
one,  and  it  may  be  that  disturbing  factors  affect  it  primarily 
and  the  other  secondarily.  I  have  not  as  yet  sufficient  evi- 
dence to  show  that  they  all  change  together  under  the  same 
influences.  In  a  number  of  the  sick  animals  I  have  found 
badly  upset  gradients  of  CO2  production,  catalase  content, 
and  latent  period,  with  a  fairly  stable  rhythmic  gradient. 
It  must  be  remembered  that  most  of  these  measurements 
were  made  on  excised  segments,  and  it  may  be  that  the 
greater  amount  of  trauma  and  handling  incident  to  the 
demonstration  of  the  first  mentioned  gradients  served  to 
bring  out  latent  weaknesses  in  the  muscle — weaknesses 
which  did  not  appear  under  the  more  advantageous  con- 
ditions supplied  while  counting  the  rates  of  contraction. 
Thus,  for  the  CO2  estimations,  the  muscle  is  stripped  from 
the  mucous  membrane  and  is  not  supplied  with  sufficient 
oxygen;  for  the  catalase  estimations  it  is  minced,  and  for 
the  latent  period  measurements  it  must  be  kept  in  a  moist 
chamber;  but  in  counting  the  rates  of  rhythmic  contraction 
one  can  use  either  the  intact  animal  with  the  abdomen 
opened  under  salt  solution,  or  excised  segments  of  bowel 
contracting  in  warm  oxygenated  Locke's  solution. 


78     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

FACTORS   ALTERING   THE    GRADIENTS 

(i)  IRRITATING  LESIONS.  These  include  traumatization, 
inflammation  and  ulceration  (a)  in  the  muscle  lining  the 
tract;  (6)  in  the  mucous  membrane;  (c)  in  the  serous  coat; 
(d)  possibly  in  the  nervous  plexus,  and  (e)  in  the  neighboring 
organs  connected  with  the  tract  such  as  the  appendix,  the 
gall-bladder,  liver,  pancreas,  and  Meckel's  diverticulum. 
We  must  think  also  of  inflammation  and  overactivity  with 
vascular  engorgement  of  the  organs  lying  close  to  the  diges- 
tive tract,  such  as  the  uterus,  the  urinary  bladder,  the 
prostate,  the  spleen,  and  perhaps  the  kidney. 

These  lesions  may  affect  (a)  the  metabolism.  It  has  been 
shown  by  Segale,395  that  inflammation  raises  the  metabolic 
rate  of  tissues.  They  become  warm  because  the  increase  in 
the  rate  of  oxidation  calls  for  a  larger  blood  supply,  and 
that  warms  the  tissues  much  as  a  heating  coil  would.  Cutting 
or  bruising  a  tissue  also  raises  its  metabolic  rate.  Thus,  in 
planarian  worms,  Child,110  found  that  cutting  increased  the 
rate  for  about  twelve  hours.  (See  also  Hyman,209  p.  76.)  We 
know  also  that  a  cut  or  bruised  part  becomes  electro-negative 
to  the  neighboring  healthy  tissue  and,  as  I  have  noted  before, 
that  indicates  an  increase  in  the  chemical  activity  (Lillie,267 
p.  181).  As  Lillie,266  (p.  441)  has  pointed  out,  local  injury 
produces  demarcation  currents  which  extend  in  both  direc- 
tions along  the  muscle.  They  exert  not  only  electrotonic 
blocking  influences,  but  they  may  directly  compensate  the 
action  current  of  an  approaching  excitation  wave  and  so 
prevent  its  effect  from  extending  beyond  the  point  of  injury. 
Garrey  has  suggested  that  this  mechanism  probably  accounts 
for  the  formation  of  heart  block  when  only  a  few  fibers  in 
the  bundle  of  His  are  injured  by  a  pinprick.  An  increase  in 
the  metabolic  rate  will  raise  (6)  the  rate  of  rhythmic  contrac- 


APPLICATION  OF  THE  GRADIENT  IDEA          79 

tion.  Taylor  and  I424  showed  that  the  rate  of  contraction  of  an 
excised  segment  of  bowel  varies  with  the  temperature  just 
as  a  chemical  reaction  will  vary.  Once,  on  opening  a  rabbit 
under  salt  solution,  I  found  a  badly  inflamed  Peyer's  patch 
in  the  ileum.  The  affected  loop  of  bowel  was  cut  out  and 
segments  of  it  were  put  into  warm  aerated  Locke's  solution. 
It  was  found  then  that  the  segment  just  above  the  lesion 
contracted  from  21'  to  25  times  per  minute,  or  more  than 
twice  as  fast  as  it  would  normally  have  done  (Alvarez,10 
p.  347).  Inflammation  ordinarily  increases  (c)  the  irritability 
of  a  tissue.  That  it  increases  (d)  the  tone  of  smooth  muscle  is 
easily  demonstrated  in  the  digestive  tract.  The  hourglass 
contraction  opposite  the  site  of  a  gastric  ulcer  is  due  partly 
to  the  increased  tone  of  the  muscle  fibers  which  are  stimu- 
lated directly  by  the  lesion.  The  same  local  action  produces 
the  puckered  and  irritable  cap  of  duodenal  ulcer,  or  the 
tightly  closed  sphincter  with  fissures  of  the  anus. 

(2)  INGESTION  OF  FOOD  WITH  DISTENTION  OF  THE  BOWEL. 
All  parts  of  the  tract  are  distended  at  times  by  gas;  the 
stomach  is  distended  by  food;  the  small  intestine  by  partly 
digested  material,  and  the  colon  by  feces,  or  by  enemas.  We 
have  seen  that  distension  of  smooth  muscle  generally  causes 
it  to  contract  more  actively.  A  greater  activity  means  (a) 
a  faster  metabolism.  That,  together  with  the  distension,  may 
increase  (6)  the  rate  oj  rhythmic  contraction.  Distension  alone 
will  increase  the  rate  in  primitive  types  of  hearts  (Straub416), 
and  I  have  some  evidence  that  the  same  thing  happens  in 
the  bowel.  I  cannot  say  as  yet  just  how  distension  and 
increased  activity  affect  (c)  the  irritability.  I  do  know  that 
after  a  loop  of  bowel  full  of  food  has  been  segmenting 
actively  for  a  while  it  gets  on  a  "hair  trigger"  so  that  a 
slight  stimulus  is  sufficient  to  start  a  peristaltic  rush.  The 


So    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

activity  incident  to  digestion  has  a  pronounced  effect  on  (d) 
the  tone.  Mall,298  p.  45,  (see  also  Cannon,87  p.  421)  pointed 
out  years  ago  that  "if  the  intestine  is  at  rest  it  is  anemic, 
small  and  long;  when  digesting  it  is  hyperemic,  large  and 
short.'*  I  have  placed  two  markers  3.5  cm.  apart  on  an  active 
and  apparently  stretched  piece  of  bowel,  and  have  found 
them  8  cm.  apart  later  when  that  region  had  emptied  and 
quieted  down.  Cannon  ascribes  some  of  this  shortening  with 
activity  to  the  "contraction  remainder"  of  smooth  muscle; 
that  is,  after  each  contraction  the  muscle  does  not  relax 
quite  to  its  previous  length. 

(3)  NERVOUS  STIMULI.  Although  the  digestive  tract  is 
largely  autonomous,  there  are  undoubtedly  many  times 
when  the  extrinsic  nerves  affect  the  progress  of  material 
through  it.  Theoretically  these  nerves  can  either  depress  or 
stimulate  the  tract  as  a  whole;  they  can  depress  or  stimulate 
one  part  more  than  another;  or  they  can  depress  in  one 
place  and  stimulate  in  another.  There  is  some  experimental 
evidence  that  vagus  stimulation  will  affect  the  two  ends  of 
the  stomach  differently  (May302).  Some  have  observed  a 
relaxation  of  the  cardia  with  an  increased  activity  near  the 
pylorus.  This  would  naturally  tend  to  reverse  the  gastric 
waves  Spadolini,406'407  has  shown  that  stimulation  of  the 
vagi  or  of  the  splanchnics  often  produces  effects  which 
are  unequal  or  dissimilar  in  different  parts  of  the  bowel. 
Similarly  in  the  heart  of  the  turtle,  the  sequence  of  the  beat 
may  be  upset  by  vagus  stimulation  which  depresses  the 
sinus  while  it  increases  the  automaticity  of  the  funnel 
region  (Gault161).  Wilson448  produced  nodal  rhythm  in  a 
number  of  young  people  by  vagus  stimulation  after  the 
giving  of  atropin.  Apparently  the  nerve  endings  in  the  A-V 
node  were  more  affected  by  the  drug  than  those  in  the  S-A 


APPLICATION  OF  THE  GRADIENT  IDEA          81 

node.  Under  these  circumstances  vagus  stimulation  would 
tend  to  reverse  the  gradient  by  depressing  the  sinus  more 
than  the  ventricle.  Lewis263  (p.  194)  states  that  vagal 
stimulation  alone  is  sufficient  to  displace  the  pacemaker  in 
some  people;  and  Miller320  (p.  411)  and  others  (Mayer304) 
have  found  that  it  will  cause  vomiting. 

There  is  considerable  evidence  for  the  view  that  a  pleasur- 
able psychic  stimulus  may  raise  the  tone,  particularly  of  the 
upper  end  of  the  tract,  and  may  improve  the  gradient.  We 
have  no  data  to  show  that  the  extrinsic  nerves  affect  (a) 
the  metabolism.  There  is  no  evidence  that  they  affect  (b) 
the  rate  of  rhythmic  contraction.  They  probably  tend 
markedly  to  depress  (c)  the  irritability,  so  that  the  muscle 
will  not  respond  to  every  stimulus.  The  most  marked  changes 
are  seen  in  (d)  the  tone. 

(4)  Toxic  DEPRESSION.  Theoretically  the  tone  and  activ- 
ity of  the  muscle  may  be  depressed  by  toxins  of  various 
kinds,  either  equally  in  all  parts,  or  to  unequal  degrees  in 
different  parts.  It  is  possible,  also,  for  a  toxin  to  depress  one 
part  while  it  stimulates  another.  If  the  depression  is  equal 
in  all  parts,  the  gradient  will  be  left  intact  and  the  progress 
of  the  food  may  be  slowed  simply  because  of  the  general 
weakness  and  sluggishness.  This  generalized  depression  may 
account  for  the  flabby  stomachs  and  intestines  which  we 
see  particularly  in  asthenic  women.  There  are  many  reasons 
for  believing,  however,  that  the  depression  is  often  uneven 
in  its  distribution,  and  likely  to  alter  the  gradient.  Time  and 
again  during  the  preceding  chapters  I  have  had  occasion 
to  remark  on  the  great  difference  in  the  hardiness  of  the 
various  muscle  strips  (Alvarez,2  p.  178  and,7  p.  426,  also,8 
p.  445,  also,10  pp.  346  and  348,  also,11  p.  189,  and,14  p.  65). 
In  the  stomach  the  muscle  at  the  pacemaking  region  near 


82     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 


the  cardia  is  most  sensitive  to  handling,  to  electric  shocks, 
to  preservation  in  the  ice-box  and  to  all  unfavorable  condi- 
tions; and  similarly  the  muscle  in  the  duodenum  is  much 
more  sensitive  to  adverse  conditions  than  is  the  muscle  in 
the  ileum.  The  muscle  of  the  colon  is  more  hardy,  again, 


Duod 


Middle 


Ileum 


FIG.  15. — Ordinates  represent  rates  per  minute;  abscissae  represent  the 
segments  at  varying  distances  from  the  pylorus.  The  solid  line  represents 
the  average  for  fifty-three  rabbits.  The  broken  lines  represent  data  from 
sickly  animals. 

than  that  of  the  small  bowel.  It  was  found  also  that  the 
gradients  of  rhythmicity,  metabolism  and  latent  period 
were  reversed  in  many  of  the  sick  animals.  Figure  15  shows 
how  the  rhythmic  gradient  may  be  altered.  The  segments 
were  removed  from  rabbits  which  were  heavily  infected 


APPLICATION  OF  THE  GRADIENT  IDEA          83 

either  with  snuffles,  coccidiosis  or  a  cecal  whipworm.  In 
these  sickly  rabbits  the  segment  excised  from  the  duodenal 
region  sometimes  would  not  contract  at  all  in  the  Locke's 
solution,  although  segments  from  the  ileum  and  colon  would 
do  so  satisfactorily.  Figure  16  shows  the  difference  between 
the  contractions  of  a  healthy  rabbit's  intestine  and  those 


FIG.  1 6. — Sample  tracings  from  segments  from  a  normal  rabbit,  on  the  left, 
and  rabbit  purged  by  castor  oil  on  the  right.  From  above  downwards  the 
records  are  from  the  duodenum,  jejunum,  upper  ileum,  lower  ileum  and  colon. 
The  time  record  represents  thirty  seconds. 

from  a  rabbit  which  had  been  purged  the  day  before  with 
magnesium  sulphate.  In  this  case  the  amplitude  is  much 
affected.  Figure  8  shows  on  the  left  side  the  usual  gradient  of 
latent  period  found  in  normal  dogs,  and  on  the  right  the 
gradient  found  in  distempered  dogs.  It  is  apparent  that 
the  muscle  in  the  duodenal  segment  suffers  most,  and  that  the 
muscle  from  the  ileum  is  even  stimulated  by  the  toxins, 


84     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

whatever  they  are.  A  similar  difference  was  observed  in  the 
stomachs  of  sick  animals;  that  is,  the  segment  from 
the  cardiac  end  would  be  insensitive  and  sluggish  while  the 
segment  from  the  pyloric  antrum  would  contract  even  more 
promptly  than  it  normally  does.  Naturally,  this  drop  in  the 
upper  end  with  a  corresponding  rise  at  the  lower  would 
tend  very  strongly  to  reverse  the  gradient. 

It  may  be  that  the  effect  of  the  toxins  is  primarily  a 
stimulating  one,  and  that  the  ileum  and  antrum  profit  by  it 
because  their  original  tone  is  low.  At  the  upper  end,  how- 
ever, the  tone  of  the  muscle  is  probably  so  nearly  maximal 
that  further  stimulation  pushes  it  over  the  limit  of  safety, 
and  the  tissue  is  damaged.  I  have  some  pharmacologic  evi- 
dence in  favor  of  such  a  view,  and  there  are  many  analogies 
in  the  biological  literature. 

Anyone  who  attempts  to  do  any  work  with  the  intestinal 
muscle  will  I  think  soon  be  impressed  with  these  marked 
changes  in  the  sickly  animals  and  will  realize  how  necessary 
it  is  in  such  experiments  to  secure  really  healthy  ones.  The 
same  precaution  must  be  taken  when  studying  the  heart.  It 
is  well  known  that  preparations  from  thin  or  sickly  animals 
or  from  animals  kept  too  long  in  the  laboratory  will  not  beat 
satisfactorily.  Frogs  and  turtles  should  not  be  used  during 
the  summer  or  during  the  mating  season  (Stiles,412  p.  341; 
Schultz,391  p.  126).  Hunter195  found  that  he  could  not  use 
Salpae  kept  in  the  laboratory  for  any  length  of  time  because 
their  hearts  beat  at  both  ends  simultaneously.  Dr.  Cohn 
of  the  Rockefeller  Hospital  tells  me  that  a  large  proportion 
of  the  dogs  studied  in  his  laboratory  show  nodal  rhythm. 
Eyster  and  Meek,146  Halsey178  (p.  731)  and  CuIIis  and 
Tribe122  remark  on  the  same  thing.  Similar  displacements  of 
the  pacemaker  have  been  observed  in  man  in  various  asthenic 
states  (Williams  and  James,447  Hart179).  The  evanescent 


APPLICATION  OF  THE  GRADIENT  IDEA          85 

nature  of  these  upsets  in  the  cardiac  gradient,  and  the  fact 
that  sometimes  at  autopsy  no  local  lesions  are  found,  makes 
me  think  that  the  displacement  of  the  pacemaker  may  be 
due  to  an  unequal  effect  of  fatigue  or  disease  toxins  on 
different  parts  of  the  heart.  It  is  well  known  to  athletes  that 
a  little  fatigue  or  infection,  a  sleepless  night,  a  slight  cold  or 
diarrhea,  will  greatly  diminish  the  efficiency  of  the  heart  and 
skeletal  muscles. 

After  I  had  for  some  time  been  studying  the  upsets  of  the 
intestinal  gradient  due  to  the  unequal  effects  of  disease 
toxins,  I  discovered  that  Dr.  C.  M.  Child  had  been  making 
similar  observations  on  the  lower  forms  of  life.  I  have  already 
reviewed  a  good  deal  of  his  work  in  the  chapter  on  gradients. 
Dr.  Child112  argues  that  tissues  with  a  high  metabolic  rate 
and  a  large  need  for  oxygen  must  suffer  more  from  a  scarcity 
of  that  oxygen  than  do  tissues  with  a  low  rate.  The  supply 
of  the  gas  can  be  curtailed  either  by  interfering  with  the 
circulation  and  pulmonary  respiration  or  by  giving  a  poison 
like  KCN  which  keeps  the  oxygen  from  combining  with  the 
protoplasm  of  the  cell  (Hyman,208  p.  340).  Child  has  found 
that  weak  solutions  of  KCN  may  be  used  very  conveniently 
to  demonstrate  the  presence  of  gradients  of  metabolism, 
because  the  tissues  with  a  high  rate  become  paralyzed  and 
die  first;  and  the  others  with  slower  rates  follow  in  order. 
Thus  if  planarian  worms  of  different  ages  are  put  into  .0065 
per  cent  KCN,  the  younger  ones  with  the  higher  rates  of 
oxidation  die  before  the  older  ones.  If  hydras  are  submitted 
to  the  same  test  the  more  active  ones  die  first.  Similarly, 
young  animals  and  babies  with  their  fast  rates  are  more 
susceptible  to  anesthetics  than  are  old  animals  and  old  men 
(Symes419).  Glaister  and  Logan167  note  also  that  in  coal 
mines  the  boys  are  more  likely  to  succumb  to  CO  poisoning 
than  are  the  older  men. 


86     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 


FIG.  17. — The  effect,  of  asphyxia  on  segments  from  different  regions.  From 
above  downward  the  segments  are  from  the  duodenum,  jejunum,  middle 
ileum  and  colon. 


APPLICATION  OF  THE  GRADIENT  IDEA          87 

Following  this  line  of  reasoning,  Child  put  into  dilute 
solutions  of  KCN  a  small  water  organism  which  swims  with 
the  help  of  comb-like  rows  of  large  cilia  which  are  arranged 
along  its  sides.  The  damaging  effect  of  the  KCN  was  so 
much  more  marked  at  the  pacemaking  end  that  the  impulse 
was  sometimes  left  to  begin  at  the  other  pole  of  the  animal; 
the  sequence  of  the  beat  was  reversed,  and  the  animal  swam 
backwards. 

After  reading  about  this  work  of  Child  I  put  five  segments 
from  different  parts  of  the  bowel  into  warm  Locke's  solution, 
and  after  they  were  all  contracting  well  I  shut  off  the  air 
which  had  been  bubbling  through  the  solution  (Alvarez 
and  Starkweather11),  Figure  17  shows  how  markedly  this 
affected  the  activity  of  the  duodenum  and  jejunum  and  how 
little  it  affected  that  of  the  ileum.  As  was  to  be  expected,  a 
trace  of  KCN  added  to  the  solution  produced  much  the 
same  type  of  graded  depression  (Fig.  18). 

It  appears  that  the  heart  muscle  also  shows  a  graded 
response  to  asphyxia.  We  would  expect  the  sensitive  pace- 
making  region  to  suffer  most,  and  actually  Lewis  and 
Mathison,265  have  found  that  the  auricle  is  slowed,  the 
ventricle  is  accelerated  and  dissociation  is  produced.  These 
changes  are  brought  about  locally,  and  are  unaffected  by 
curare,  atropin  and  vagal  section.  On  the  return  of  respi- 
ration, recovery  is  generally  prompt  and  complete.  Similarly, 
in  hibernating  dormice  Miss  Buchanan76  found  that  the 
ventricles  beat  alone,  but  as  the  animal  wakes  and  begins  to 
breathe  more  rapidly,  the  P  waves  (auricular)  appear  in  the 
electrocardiogram.  After  a  while  the  gradient  is  restored 
and  the  auricle  takes  the  pace.  When  the  animal  breathes  in 
Cheyne-Stokes  fashion,  the  P  waves  disappear  during  the 
periods  of  apnea.  Greene  and  Gilbert169  found  also  while 
studying  the  hearts  of  aviators  subjected  to  the  rebreathing 


88     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

test,  that  when  the  oxygen  supply  was  greatly  lowered  the 
S-A  region  was  the  first  to  fail. 


FIG.  18. — Effect  of  KCN  on  segments  in  non-oxygenated  Locke's  solution. 
At  A  air  was  allowed  to  bubble  through  the  solution;  At  B,  more  KCN  was 
added. 

Raasche370  has  shown  with  the  excised  heart  that  chloro- 
form can  paralyze  the  auricle  in  dosages  which  only  decrease 


APPLICATION  OF  THE  GRADIENT  IDEA          89 

the  amplitude  of  the  ventricular  contractions,  and  it  may 
be  that  some  of  the  stoppages  of  that  organ  after  anesthesia 
are  due  partly  to  a  reversal  of  the  rhythmic  gradient  (Fig. 
19).  Some  of  the  other  cardiac  poisons,  and  perhaps  some 
of  the  disease  toxins  show  signs  of  acting  in  this  disturbing 
way. 

Tashiro422    has    recently    brought    forward    considerable 
evidence   to   show  that   anesthesia,   particularly  in  nerve 


FIG.  19. — The  upper  tracing  is  from  the  left  ventricle;  the  lower  is  from  the 
left  auricle.  Time  marking  represents  records.  Note  greater  effect  of 
chloroform  on  the  auricle.  (From  Raascbe.) 

trunks,  may  be  due  to  a  similarly  produced  reversal  in  the 
metabolic  gradient  along  the  nerves.  Much  work  must  yet 
be  done  before  such  a  theory  will  be  generally  accepted,  but 
in  view  of  the  many  analogies,  the  idea  is  a  very  attractive 
one.  He  explains  perfectly  some  of  the  puzzling  phenomena  of 
conduction  through  anesthetized  stretches  (Niwa342).  There 
are  so  many  practical  applications  of  this  idea  of  gradient 
reversal  under  the  action  of  drugs  and  toxins,  that  I  believe 
it  must  be  used  more  and  more  as  men  come  to  know  about 
it.  It  offers  the  simplest  and  easiest  explanation  for  many 
phenomena  which  have  hitherto  been  explained  in  round- 
about ways,  as  by  bringing  in  a  complicated  system  of 
nerves,  the  workings  of  which  are  not  really  understood. 


90     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

I  think  there  is  no  doubt  that  digestive  upsets  in  the  sick 
are  due  in  part  to  influences  coming  through  the  extrinsic 
nerves,  but  when  one  can  demonstrate  a  marked  reversal 
of  the  gradient  in  small  excised  segments  of  gut,  and  when 
one  can  tell  by  studying  such  segments  whether  they  have 
been  removed  from  a  sick  or  from  a  healthy  animal,  I  think 
the  most  devoted  follower  of  Eppinger  and  Hess142  must 
admit  that  the  local  changes  have  some  significance.  I 
believe  that  the  upsets  in  the  gradient  which  are  so  easily 
demonstrated  can  explain  the  loss  of  appetite,  the  disgust  for 
food,  the  nausea  and  the  vomiting  seen  in  infectious  diseases 
and  asthenic  states.  The  distempered  dogs  and  snuffling 
cats  often  refuse  food.  If  some  is  forced  on  them  it  may  stay 
in  the  stomach  for  hours  or  days.  This  has  been  commented 
upon  by  Cannon  and  others.  In  autopsies  on  people  who 
have  died  with  botulism,  food  has  been  found  in  the  stomach 
which  was  eaten  many  days  before,  when  the  trouble  com- 
menced. Similar  stagnation  is  often  noticed  in  the  stomachs 
of  men  and  women  with  tuberculosis  and  other  infectious 
diseases.  As  in  many  of  these  cases  I  find  the  pylorus  patent 
and  can  see  good  peristaltic  waves,  I  cannot  get  away  from 
the  idea  of  a  flattened  gradient.  Later  when  such  patients 
go  on  vacations,  take  rest  cures  or  get  over  their  infections, 
their  appetities  return,  they  are  able  to  digest  the  roughest 
food;  and  I  believe  their  gradients  have  become  normally 
steep  again. 

It  is  well  known  to  all  clinicians  that  most  men  with 
failing  hearts  have  indigestion  and  flatulence.  Remembering 
the  upsetting  effect  of  asphyxia  on  the  gradient,  it  has 
occurred  to  me  that  a  chronic  passive  congestion,  interfering 
with  the  oxygen  supply  to  the  intestinal  muscle,  might 
easily  account  for  much  of  the  trouble.  It  is  possible,  of 
course,  that  some  of  the  disturbance  is  due  to  stimuli  coming 


APPLICATION  OF  THE  GRADIENT  IDEA          91 

down  the  vagus,  but  we  know  much  less  about  the  way  in 
which  such  stimuli  act  than  we  know  about  the  way  in 
which  asphyxia  acts.  Nausea  is  often  a  marked  symptom  in 
acute  decompensations  of  the  heart,  and  in  a  subsequent 
chapter  the  reasons  will  be  given  for  believing  that  that 
means  mild  reverse  peristalsis.  Nausea  and  vomiting  are 
prominent  symptoms  also  in  subacute  CO  poisoning,  in 
which  case  the  intestine  must  share  in  the  general 
asphyxiation  of  the  tissues. 

(5)  DRUGS.  Very  little  is  known  as  yet  about  the  effects 
of  drugs  on  the  gradient.  This  is  due,  of  course,  to  the  fact 
that  it  has  not  yet  occurred  to  pharmacologists  that  a  drug 
might  upset  the  dynamic  equilibrium  of  the  intestine  by 
stimulating  or  depressing  one  part  more  than  another-  To 
be  sure,  we  speak  of  certain  purgatives  as  acting  principally 
on  the  small  bowel  or  on  the  large,  but  after  reading  very 
extensively  on  the  subject,  I  can  find  no  statement  which 
suggests  that  any  one  has  thought  of  purgation  as  being  due 
to  a  lowering  of  the  tone  of  the  lower  end  of  the  colon. 

Figure  20  shows  that  the  action  of  adrenalin  on  the  intes- 
tinal muscle  is  a  purely  depressant  one,  and  that  it  is  graded 
from  duodenum  to  ileum.  I  was  able  to  show  that  it  is  a 
depressant  also  when  given  intravenously  to  man,  and  yet 
we  know  that  it  often  acts  as  a  purgative.  In  a  woman  with 
a  large  ventral  hernia,  which  left  the  ileum  easily  visible 
under  a  thin  covering  of  skin,  adrenalin  produced  a  transient 
cessation  of  rhythmic  movements  which  was  followed  by 
the  appearance  of  some  peristaltic  rushes,  and  later  by  a 
summons  to  empty  the  bowel.  It  seemed  to  me  that  the 
rush  waves  might  have  been  brought  about  by  an  unbalanced 
condition  of  the  gut  due  to  the  persistence  of  activity  in  the 
duodenum  at  a  time  when  the  ileum  and  colon  were  paralyzed. 
Magnesium  sulfate  is  another  muscular  depressant 


92     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

which  shows  a  graded  effect  on  the  segments,  and  which 
purges.    Here,    however,    the    pronounced    effects    on    the 


FIG.    20. — The    graded   effect  of  adrenalin.     From    above  downwards,  the 
segments  are  from  duodenum,  upper  ileum,  lower  ileum  and  colon. 

absorption  of  fluid  from  the  mucous  membrane  are  probably 
much  more  important  factors  in  producing  the  diarrhea. 


APPLICATION  OF  THE  GRADIENT  IDEA          93 

I  have  studied  the  effects  of  some  seventy-five  different 
drugs  on  excised  segments  from  different  parts  of  the  bowel, 
(Alvarez,12  and  also16)  and  have  found  definite  regional 
differences  with  many  of  them.  Much  work  must  yet  be 
done,  particularly  on  the  intact  animal,  before  we  can  say 
whether  these  differences  have  any  practical  significance. 
It  is  only  suggestive  that  a  number  of  the  drugs  whose 
action  on  the  segments,  if  duplicated  in  the  intact  animal, 
would  tend  to  reverse  the  gradient,  are  emetics;  and  many 
of  those  that  would  tend  to  steepen  it  are  well  known  laxa- 
tives. Pharmacologists  would  probably  remind  me  that 
almost  all  of  the  emetics  have  been  shown  to  act  directly  on 
the  vomiting  center  in  the  medulla.  Eggleston  and  Hatcher135 
have  shown  conclusively  that  even  an  eviscerated  dog  which 
has  no  digestive  tract  between  his  diaphragm  and  his  anus 
will  retch  when  given  apomorphin.  It  is  worth  noting, 
however,  that  some  of  the  drugs,  which  in  large  doses 
produce  emesis,  in  small  doses  produce  regurgitation,  heart 
burn,  belching  and  nausea,  which  as  I  shall  show  later,  are 
probably  signs  of  mild  reverse  peristalsis.  It  seems  to  me 
that  these  drugs  may  perhaps  first  reverse  or  flatten  the 
gradient  in  the  bowel;  and  that  the  disturbances  thus 
produced  may  finally  so  influence  the  center  in  the  brain 
that  it  calls  into  action  the  voluntary  muscles  and  brings 
about  the  coordinated  vomiting  movements. 

It  is  interesting  that  the  ancients  used  purgatives  to 
restore  the  downward  gradient  after  they  had  produced  too 
violent  and  too  lasting  an  emesis,  and  similarly  they  gave 
emetics  to  try  to  stop  violent  purgation.  When  the  ancient 
Egyptians  wanted  to  see  if  a  woman  was  pregnant  they 
gave  her  pounded  watermelon  in  milk.  If  she  vomited,  the 
test  was  supposed  to  be  positive  (Neuberger340).  Possibly 
a  mild  emetic  insufficient  to  turn  a  healthy  person's  stomach 


94     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

might  be  sufficient  to  reverse  peristalsis  in  a  woman  whose 
gradient  was  already  somewhat  upset  by  the  pregnancy. 
As  I  shall  point  out  later,  there  is  some  evidence  that  the 
gradient  is  actually  flattened  or  reversed  in  some  pregnant 
women. 

I  think  it  is  quite  possible  that  certain  laxatives,  especially 
calomel,  help  the  "bilious"  not  because  of  any  action  on  the 
.liver,  because  that  has  been  pretty  thoroughly  disproved; 
but  by  restoring  the  downward  gradient  which  has  been 
upset,  perhaps  by  the  overactivity  of  a  distended  colon. 
It  may  be  that  drugs  like  eserin  and  pilocarpin  which  produce 
active  peristalsis  do  not  serve  well  as  purgatives  because 
they  stimulate  all  parts  of  the  tract  equally.  Katsch226 
(p.  287)  who  watched  the  contractions  of  the  bowel  through 
glass  windows  in  the  abdominal  wall,  was  impressed  with  the 
fact  that  although  these  drugs  greatly  increased  the  activity 
of  the  muscle,  they  did  not  cause  much  movement  of  material 
from  one  loop  to  another. 

WAYS  IN  WHICH  THE  VARIOUS  FACTORS  CAN  ALTER  THE 
GRADIENT.  Theoretically  the  gradient  as  a  whole  may  be 
made  more  steep,  less  steep,  level  or  reversed.  Each  of  these 
changes  may  be  brought  about  in  three  different  ways. 
Thus,  the  gradient  may  be  steepened  by  raising  the  upper 
end,  by  depressing  the  lower  end,  or  by  doing  both  at  the 
same  time.  The  gradient  may  also  be  altered  in  sections. 
Thus  in  cases  of  vomiting  with  diarrhea  it  may  be  that  some 
point  in  the  middle  of  the  bowel  has  become  very  irritable 
so  that  the  gradient  slopes  away  from  it  in  both,  directions. 
A  lesion  producing  a  slighter  degree  of  local  irritability  may 
make  only  a  small  "hump."  The  gradient  might  also  be 
interrupted  by  what  may  perhaps  be  termed  "deep  holes." 
Thus  in  a  number  of  purged  rabbits,  short  sections  of  bowel 


APPLICATION  OF  THE  GRADIENT  IDEA          95 

were  found  which  would  not  react  at  all  to  strong  electric 
currents  or  pinches,  while  the  adjacent  bowel  on  either  side 
was  very  irritable.  Theoretically  food  and  gas  might  become 
trapped  for  a  while  in  such  weakened  segments  (Alvarez  and 
Taylor23). 

STIMULATION  AT  THE  UPPER  END  WITH  POSSIBLE  STEEPEN- 
ING OF  THE  GRADIENT.  It  may  sound  like  a  Hibernianism, 
but  it  does  seem  that  food  goes  down  the  tract  more 
easily  because  it  is  put  in  at  the  upper  end.  A  rise  of  tone  in 
the  stomach  and  duodenum  tends  to  make  the  gradient  of 
forces  steeper  down  the  bowel.  There  is  some  evidence  that 
a  barium  meal  will  go  down  the  bowel  faster  if  it  is  follow- 
ed by  a  second  meal  given  shortly  afterwards  (Hurst,202 
Ludin281).  The  second  meal  probably  tends  to  maintain  the 
high  tone  at  the  upper  end.  There  is  also  considerable  evi- 
dence that  pleasurable  psychic  stimuli  still  further  raise 
this  tone.  Several  observers  have  stated  that  contrast  meals 
leave  the  stomach  more  rapidly  if  they  are  made  palatable 
(Hurst,202  Gilmer165).  Haudek  and  Stigler180  (p.  159)  thought 
that  the  emptying  of  the  stomach  was  slower  when  the  food 
was  taken  with  disgust.  Takahashi421  showed  that  a  cat's 
stomach  emptied  half  as  fast  when  the  animal  was  fed  with 
a  spoon  as  when  it  ate  by  itself.  Sailer  (Worden  et  al.452) 
thought  that  the  bismuth  meal  left  the  stomach  more  quickly 
when  the  patient  drank  it  than  when  it  was  given  by  stomach 
tube.  I  observed  in  a  patient  with  a  jejunal  fistula  that  the 
contractions  of  the  bowel  were  more  active  when  the  patient 
ate  by  himself  than  when  a  nurse  fed  him.  The  latter  method 
of  eating  was  plainly  annoying  to  him.  One  of  my  patients 
with  an  incompetent  anal  sphincter  generally  had  one  or 
more  bowel  movements  immediately  after  either  eating, 
smelling,  seeing  or  even  thinking  pleasurably  of  food.  It 


96     THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

has  been  shown  that  sham  drinking,  particularly  in  thirsty 
animals,  will  cause  water  to  leave  the  stomach  of  a  dog 
much  faster  than  it  otherwise  would  (Best  and  Cohnheim,52 
p.  1 1 6).  The  dog  drinks  in  the  usual  way,  but  the  water  runs 
out  through  an  esophageal  fistula  in  the  neck.  The  water  in 
the  stomach  is  put  in  through  a  gastrostomy  opening. 
Such  sham  feeding  will  also  prevent  the  backflow  into  the 
stomach  which  occurs  when  fat  is  introduced  into  the 
duodenum  through  a  fistula  (Best  and  Cohnheim,51  p.  125). 
This  is  explainable  if  the  plesaure  of  drinking  has  caused  the 
tone  of  the  stomach  to  rise  above  that  of  the  duodenum. 

Jonas,218  several  years  ago  remarked  on  the  rapid  progress 
of  food  through  the  small  intestine,  and  the  diarrhea  which 
may  appear  when  the  stomach  empties  too  rapidly.  Hence 
he  speaks  of  the  stomach  as  the  "Hauptmotor"  for  the 
intestine.  (See  also  Surmont  and  Dubus.417)  A  similar  hyper- 
motility  with  even  fatal  diarrhea  has  been  observed  occasion- 
ally after  gastro-enterostomies  when  the  stomach  emptied 
too  rapidly  (Hurst,204  p.  466;  Moynihan,330  p.  221).  This 
steepening  of  the  gradient  by  rapid  overdistension  of  the 
duodenum  may  be  largely  responsible  for  the  diarrhea  of 
people  with  achlorhydria.  The  reason  that  it  occurs  generally 
in  the  morning  may  be  that  the  bowel  is  then  most  irritable 
and  responsive  on  account  of  the  night's  rest.  There  may,  of 
course,  be  other  factors — the  intestinal  contents  may  be 
more  stimulating  on  account  of  defective  chemical  digestion, 
abnormal  temperature,  abnormal  osmotic  pressure,  or  ab- 
normal bacterial  content. 

If,  on  the  other  hand,  the  gastric  peristalsis  is  weakened 
and  the  emptying  of  the  stomach  slowed,  the  progress  of 
material  through  the  bowel  is  often  slowed.  Dagaew126 
found  in  dogs  that  when  the  strong  antral  muscle  is  removed, 
the  food  reaches  the  lower  ileum  in  thirteen  hours  instead 


APPLICATION  OF  THE  GRADIENT  IDEA          97 

of  six.  Similarly,  in  a  human  case,  Cohn115  found  that  after 
complete  removal  of  the  stomach  and  vagus  endings  the 
food  took  twenty-four  hours  to  reach  the  cecum.  Cole119 
(p.  no)  has  remarked  also  on  the  slow  emptying  of  the 
cecum  if  the  patient  fasts  after  taking  a  barium  meal. 

There  is  some  evidence  that  actual  reversal  of  the  gra- 
dient may  take  place  during  starvation  if  the  tone  of  the 
upper  end  of  the  tract  falls  markedly.  This  may  account  for 
the  nausea  experienced  by  many  people  when  they  are 
hungry.  Boldireff62  states  that  in  animals  which  have  fasted 
for  some  time,  intestinal  juice  will  run  out  of  a  gastric 
fistula  continuously  in  large  amounts. 

There  is  no  doubt  that  irritant  lesions  increase  the  tone 
and  activity  of  the  upper  end  of  the  tract.  In  the  presence 
of  a  duodenal  ulcer,  not  only  the  duodenum,  but  the  whole 
stomach  often  becomes  irritated  so  that  it  shows  four  or  five 
waves  at  a  time.  A  similar  hypermotility  is  observed  in 
some  cases  of  gall-bladder  disease.  In  these  cases  the  head  of 
the  barium  column  is  often  found  at  the  splenic  flexure 
after  six  hours,  which  is  exactly  what  we  would  expect  if  the 
gradient  has  been  steepened. 

Theoretically  a  duodenal  or  pyloric  ulcer  should  slow  the 
progress  of  material  coming  towards  it  from  the  stomach, 
and,  when  irritant  enough,  it  should  reverse  the  gastric 
waves.  Actually  we  do  find  in  many  of  these  cases  a  six-hour 
residue  in  the  stomach  and,  more  rarely,  we  see  the  reverse 
waves.  Occasionally  I  have  seen  wave-like  contraction  rings 
arising  in  the  stomach,  perhaps  moving  downwards  a  few 
centimeters  and  then  fading  out  as  if  they  were  blocked 
from  advancing  farther.  Unfortunately  the  picture  is  com- 
plicated by  a  number  of  factors.  One  of  these  is  probably  the 
connective  tissue  barrier  at  the  pylorus.  As  that  line  of 
division,  together  with  the  difference  in  the  muscle  on  the 


98    THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

two  sides,  stops  the  progress  of  waves  downward,  it  probably 
tends  to  block  some  of  the  influences  passing  upwards. 
Many  of  the  six-hour  residues  are  due  almost  entirely  to  a 
mechanical  blocking  of  the  pylorus  by  the  lesion.  In  other 
cases  we  find  that  the  stomach  empties  unusually  rapidly 
during  the  first  few  minutes,  and  after  that,  there  is  marked 
stagnation  for  hours.  In  these  cases,  it  seems  to  me  that  the 
hypertonic  stomach,  distended  and  stimulated  by  the  food, 
is  able  to  overcome  the  back  pressure  from  the  ulcer.  After 
that  stimulus  is  partly  gone,  the  irritation  of  the  ulcer,  with 
the  change  in  the  gradient,  is  able  to  hold  back  a  residue  in 
the  stomach,  perhaps  until  that  organ  is  sufficiently 
distended  again  by  food. 

When  a  stomach  is  greatly  distended,  owing  to  the  pres- 
ence of  a  stenosing  ulcer  at  the  pylorus,  the  point  of  origin 
of  the  waves  may  be  affected  also  by  differences  in  the 
pressure  sustained  by  different  parts  of  the  muscular  wall. 
Other  factors  will  be  found  discussed  in  Chapter  VIII. 
Carcinoma  ordinarily  seems  to  grow  without  irritating  the 
surrounding  muscle  very  much;  in  fact,  it  may  even  depress 
it.  Hence  it  is,  perhaps,  that  the  gradient  often  remains 
normal,  and  symptoms  are  not  produced  until  the  tumor 
acts  mechanically. 

THE  MECHANICAL  CONTROL  OF  THE  PYLORUS.  The  idea 
of  a  gradient  is  helpful  also  in  studying  the  peculiarities  of 
pyloric  action,  particularly  in  disease.  Cannon83  showed 
many  years  ago  that  one  of  the  factors  controlling  the 
sphincter  is  a  chemical  one;  that  is,  an  increase  in  the  acidity 
of  the  stomach  tends  to  open  the  pylorus,  and  an  increase 
in  the  acidity  of  the  duodenum  tends  to  close  it.  This  mechan- 
ism seems  so  simple  and  so  appropriate  that  some  writers 
make  the  mistake  of  considering  it  to  be  the  only  factor  at 


APPLICATION  OF  THE  GRADIENT  IDEA          99 

work.  This  is  in  spite  of  Cannon's82  (p.  570)  statement 
that  "in  whatever  manner  the  pylorus  may  act  under 
normal  conditions,  that  action  can  certainly  be  overcome  in 
abnormal  states."  Cannon  realized  that  his  experiments  did 
not  throw  light  on  some  of  the  peculiarities  of  gastric  empty- 
ing in  achylia  and  in  the  presence  of  ulcers  and  carcinomas. 
Recently  a  great  deal  of  the  theorizing  based  upon  the  idea 
of  an  alkaline  duodenum  has  been  upset  by  the  work  of 
McCIendon,309  Long  and  Fenger,273  and  others  who  have 
shown  with  the  help  of  modern  electro-chemical  methods, 
that  the  contents  of  the  upper  intestine  are  normally  slightly 
acid.  In  animals  with  short  intestines  they  may  be  acid 
even  as  far  as  the  ileocecal  sphincter.  Furthermore,  a  number 
of  those  who  in  recent  years  have  studied  the  emptying  of 
the  stomach  in  man  have  come  to  the  conclusion  that 
especially  in  disease,  the  hydrochloric  acid  has  little  to  do 
with  the  pyloric  control  (Von  Bergmann,49  Faulhaber  and 
von  Redwitz,149  Egan,134  Morse,328  Wheelon  and  Thomas,444 
Luckhardt,  Philips  and  Carlson,277  McCIure,  Reynolds  and 
Schwartz,311  Spencer,  Meyer,  Rehfuss  and  Hawk,408  Lenk 
and  Eisler260). 

It  seems  probable,  from  a  great  deal  of  experimental 
work,  that  the  opening  and  closing  of  the  pylorus  depends 
to  a  large  measure  on  mechanical  factors,  that  is,  differences 
in  the  gradient  of  tone  and  irritability  between  the  stomach 
and  duodenum.  I  have  already  mentioned  the  experiments 
which  show  that  an  increased  pressure  brought  about  by 
pleasant  psychic  influences  will  cause  more  rapid  emptying. 
An  increase  in  the  amount  of  distension  of  the  stomach  may 
have  a  similar  effect.  Thus  Marbaix300  found  that  250  c.c. 
of  water  left  his  stomach  twice  as  fast  if  he  put  250  c.c.  of  air 
on  top  of  it.  Ludin,281  Moritz,327  and  others  have  found  that 
food  eaten  on  top  of  a  contrast  meal  causes  that  to  leave 


ioo  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

the  stomach  more  rapidly.  Cohnheim  and  Dreyfus118 
(p.  58)  found  in  the  dog  that  when  little  food  was  present  in 
the  stomach  10  c.c.  of  gastric  contents  injected  into  the 
duodenum  through  a  fistula  closed  the  pylorus  for  from  ten  to 
fifteen  minutes;  but  when  the  stomach  was  full  of  fluid,  the 
same  stimulus  stopped  the  flow  for  from  one  to  one  and 
one-half  minutes.  The  distension  of  the  duodenum  by  a 
balloon  (Tobler426)  or  by  food,  or  the  irritation  of  the  bowel 
by  strong  saline  solutions,  retarded  the  emptying  of  the 
stomach.  Cohnheim  and  Dreyfus118  (p.  58)  put  4  per  cent 
solutions  of  sodium  chloride  and  magnesium  sulphate 
through  a  fistula  into  the  upper  bowel  and  produced  marked 
slowing  of  gastric  emptying,  nausea  and  even  vomiting. 
Baumstark37  produced  a  similar  slowing  when  he  put  fer- 
mented food  through  fistulae  into  different  parts  of  the 
small  intestine.  Similarly  no  food  left  the  stomach  of  an 
animal  for  five  hours  after  Cannon  and  Murphy93  (p.  515) 
made  an  entero-enterostomy  18  cm.  below  the  pylorus.  All 
these  procedures  probably  raised  the  tone  of  the  intestine 
above  that  of  the  stomach.  When  the  bowel  quieted  down 
or  partially  emptied  itself  of  food  the  stomach  was  able 
to  empty  again.  It  is  this  type  of  activity  which  keeps  the 
food  from  pouring  out  of  the  stomach  after  gastro-enter- 
ostomies  and  pyloroplasties  (Cannon  and  Blake,92  p.  708; 
Marbaix,300  p.  283;  von  Gehuchten,163  p.  277).  If  this  retard- 
ing effect  from  the  bowel  is  eliminated  by  allowing  the  food 
to  escape  through  a  duodenal  fistula,  the  stomach  empties 
very  rapidly  (Hirsch,189  p.  382). 

Towards  the  close  of  a  meal  or  during  starvation  it  appears 
that  the  tone  of  the  stomach  drops  below  that  of  the  digesting 
bowel,  because  we  know  that  the  duodenal  contents  then 
flow  back  into  the  stomach  (Kussmaul,247  Rehfuss,  Bergheim 
and  Hawk372).  This  back-flow  can  be  accentuated  by  eating 


APPLICATION  OF  THE  GRADIENT  IDEA      ;'iitf 


fats  (BoIdirefF,62  p.  457),  perhaps  because  while  they  impair 
the  tone  and  motility  of  the  stomach  (von  Tabora,420 
Cannon,83  p.  315)  their  fatty  acids,  split  off  by  the  pancreatic 
juice,  stimulate  the  bowel  (Bokai61).  Neilson  and  Lipsitz339 
have  shown  also  that  bodily  activity  and  posture  have  some 
effect  on  the  emptying  time  of  the  stomach. 

Stimulation  in  the  Middle.  We  have  seen  that  a  stimulus 
which  raises  the  tone  in  the  middle  of  a  loop  sends  off  waves 
in  both  directions.  Hence  it  is  not  surprising  that  food  put 
into  the  middle  of  the  tract  tends  to  go  both  ways.  Thus  in 
jejunal  feeding,  unless  the  food  is  put  in  very  slowly  and 
exactly  at  the  body  temperature,  there  will  often  be  nausea, 
regurgitation  of  the  material,  and  even  vomiting  (Kelling,234 
p.  248;  Wegele,  Gross  and  Held,442  p.  272;  Stockton,413  p.  81). 
In  some  cases  observed  by  me  the  patient's  discomfort  was 
relieved  only  by  giving  a  little  food  by  mouth  just  before 
the  feedings.  This  perhaps  raised  the  tone  of  the  stomach 
to  its  normal  position  above  that  of  the  jejunum.  In  a 
case  of  jejunal  feeding,  nausea,  vomiting  and  colic  were 
produced  by  giving  a  Murphy  drip  of  glucose  and  salt 
solution.  When  this  was  stopped,  the  patient  had  no  further 
distress  until  one  day  when  he  had  a  cleansing  enema.  In 
that  case  the  lower  end  of  the  gradient  was  probably  raised 
too  high.  It  is  common  knowledge  that  vomiting  is  often 
associated  with  diarrhea.  Thus,  a  small  boy  who  had  eaten 
his  fill  of  black-berries  vomited  three-fourths  of  the  amount 
twelve  hours  later,  and  shortly  after  that  the  remainder 
was  voided  in  loose  bowel  movement.  Probably  enough  of 
the  irritant  material  got  into  the  jejunum  at  the  start  to 
raise  the  irritability  there  and  to  prevent  the  stomach  from 
emptying.  Finally  the  tone  became  high  enough  in  the  upper 
bowel  so  that  it  could  clear  itself  in  both  directions.  The 
vomiting  and  diarrhea  with  seasickness,  or  after  strong 


OF  THE  DIGESTIVE  TRACT 

psychic  stimulation  might  be  due,  at  least  in  part,  to  a  rise 
in  tone  of  the  jejunum  at  the  point  where  it  is  so  richly 
supplied  with  vagus  fibers  (Bayliss  and  Starling,39  p.  141; 
Colin  Mackenzie,286  and  also287  p.  287,  Jacob},213  p.  198). 

Lesions  in  the  course  of  the  bowel  may  make  the  affected 
area  so  irritable  that  the  barium  meal  will  stay  out  of  it 
(Stierlin411).  Thus  Kienbock,235  and  Case106  (p.  381)  have 
remarked  on  the  emptiness  of  the  cecum  in  cecal  tubercu- 
losis. Nothnagel345  (p.  39)  found  that  food  was  rushed 
through  sections  of  bowel  which  he  irritated  by  the  injection 
of  concentrated  salt  solution,  and  White445  made  similar 
observations  with  croton  oil. 

If  the  gradient  is  reversed  above  an  irritated  place  in 
the  bowel,  as  the  theory  demands,  we  should  expect  the 
"reversed"  segment  to  remain  empty,  and  actually  we  do 
find  that  food  does  not  pack  up  against  an  intestinal  ob- 
struction unless  it  is  due  to  a  carcinoma  or  some  other 
slowly  arising  and  non-irritating  cause,  i.e.,  something 
which  does  not  affect  the  gradient  (Kirstein,237  Kelling,234 
Maleyx,297  Reichel,373  Nothnagel,343  p.  29;  Quirot,388  p.  25; 
Shimodaira399).  The  more  irritating  the  lesion,  the  wider 
the  empty  zone,  and  the  farther  orad  do  we  find  the  signs  of 
back-pressure.  Years  ago  Kirstein237  came  to  the  conclusion 
that  the  symptoms  of  acute  ileus  are  not  the  result  of 
closure  of  the  bowel  but  of  its  maltreatment.  When 
he  cut  the  ileum  across  and  sewed  it  up,  food  went  on 
down  and  packed  against  the  obstruction;  the  dogs  did 
not  vomit  and  did  not  seem  sick.  When,  however  he 
pinched  the  bowel  with  an  elastic  ligature  the  food  was 
held  back  far  above  the  lesion  and  the  dogs  were  very  sick. 
Treves434  (p.  2)  noted  also  that  in  acute  intussusception 
violent  symptoms  of  obstruction  often  appear,  although  at 
operation  little  narrowing  is  found  in  the  lumen  of  the  bowel. 


APPLICATION  OF  THE  GRADIENT  IDEA         103 

In  other  cases  of  intestinal  obstruction  no  organic  narrowing 
can  be  found,  and  the  cause  is  said  to  be  "dynamic."  The 
following  experiment  shows  that  intestinal  obstruction  can 
occur  without  any  narrowing  of  the  lumen  at  all.  I 
took  a  rabbit's  intestine,  exposed  under  salt  solution, 
and  pinched  the  lower  ileum  with  a  hemostat,  so  as  to 
bruise  a  narrow  ring.  The  diameter  of  the  lumen  was  in  no 
way  altered.  The  abdomen  was  closed.  The  animal  was 
kept  under  urethan  anesthesia,  and  was  opened  again 
several  hours  later.  It  was  then  found  that  no  food  had 
passed  the  injured  place,  although  the  bowel  above  was 
markedly  distended  and  was  contracting  violently.  Waves 
approached  within  10  or  15  cm.  of  the  site  of  the  lesion,  where 
they  either  faded  away  or  broke  against  reverse  waves. 
The  bowel  immediately  above  the  lesion  contained  only  a 
little  gas.  I  concluded  that  the  gradient  was  uphill  for  some 
distance  above  the  bruised  tissue.  Kelling234  was  actually 
able  to  show  such  a  reversal  by  tying  manometers  into 
the  bowel  at  different  levels  above  an  experimentally  pro- 
duced obstruction. 

The  fact  that  the  segment  of  bowel  immediately  above 
the  site  of  obstruction  contains  nothing  but  gas  has  been 
commented  upon  by  some  surgeons  who  have  come  to  the 
conclusion  that  in  bad  cases,  enterostomies  should  be  made 
high  above  the  lesion  if  any  drainage  of  fluid  is  to  be  expected. 
Other  surgeons  have  noticed  that  gastric  stasis  and  dilation 
appear  early  in  the  course  of  intestinal  obstruction.  They 
have  washed  large  amounts  of  intestinal  contents  out  of  the 
stomach  some  time  before  the  reversal  of  the  gradient  was 
marked  enough  to  produce  fecal  vomiting  (Ewald,144). 
We  see  then  that  the  gradient  idea  throws  great  light  on  the 
peculiarities  of  intestinal  action  in  ileus,  and  in  its  turn, 
receives  much  support  and  confirmation. 


io4   THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

Stimulation  at  the  Lower  End.  The  commonest  lesion 
found  at  the  lower  end  of  the  small  intestine  is  appendicitis. 
This  disease  can  produce  all  grades  of  back  pressure  from 
a  slight  ileac  stasis,  demonstrable  by  the  roentgen  ray, 
to  the  vomiting  of  large  amounts  of  intestinal  fluid.  Just  as 
the  emptying  of  the  stomach  tends  to  produce  an  emptying  of 
the  lower  ileum  into  the  cecum  (Hurst,199  p.  34,  also,203 p.  55), 
so  it  appears  that  an  early  emptying  of  the  ileum  may  favor 
the  emptying  of  the  stomach,  and  a  late  emptying  of  the 
ileum  may  slow  the  emptying  of  the  stomach  (Cole,119 
p.  109,  Barclay,35  p.  643).  Considerable  experimental 
work  has  been  done  on  the  subject  by  Hedblom  and  Cannon, 18  2 
and  later  by  White.445  They  found  in  cats  that  they  could 
slow  the  progress  of  food  through  the  stomach  and  small 
intestine  if  they  irritated  the  cecum  sufficiently  with  croton 
oil.  Mild  degrees  of  irritation  produce  no  effect  on  the  empty- 
ing of  the  stomach.  Similarly  in  man,  much  depends  upon  the 
degree  of  irritation  produced  by  the  lesion;  upon  the  stage  in 
which  we  find  the  disease,  and  upon  the  original  stability  of 
the  gradient  in  a  particular  individual  (Borgbjarg,64  Barclay,34 
p.  234;  Paterson,352  p.  197;  Smithies,404  p.  187).  Thus  in  an 
interval  between  attacks  we  may  be  unable  to  detect  any 
abnormality  in  the  fluoroscopic  picture;  in  a  subacute  case 
there  may  be  loss  of  appetite,  nausea  and  some  gastric 
and  duodenal  stasis,  and  in  an  acute  case  there  may  be 
persistent  vomiting.  I  remember,  however,  a  strong,  stout 
young  woman,  with  a  good  appetite,  who  walked  around 
for  several  days  with  an  "exploded"  appendix.  Even 
during  the  height  of  her  pain  she  had  no  nausea,  she 
did  not  vomit,  her  appetite  remained  good  and  she  noticed 
only  a  coated  tongue,  bad  taste,  a  tendency  to  fill  up 
quickly  after  eating,  and  some  diarrhea.  Apparently  the 
gradient  of  this  robust  girl  was  so  good  that  even  a  pericecal 


APPLICATION  OF  THE  GRADIENT  IDEA         105 

abscess  could  not  reverse  it.  All  it  could  do  was  to  steepen 
the  gradient  below  the  lesion.  Theoretically,  we  should  always 
find  a  more  rapid  emptying  of  the  colon  with  appendicitis, 
and  we  do  see  it  quite  often  in  children.  According  to  Deaver124 
(p.  226  and  244),  it  is  present  in  adults  in  only  13  per  cent 
of  the  cases.  Apparently  other  factors  come  in  to  neutralize 
the  tendency. 

Some  of  the  most  violent  forms  of  reverse  peristalsis 
in  the  tract  are  due  to  the  irritation  of  the  sigmoid  flexure 
caused  by  volvulus.  I  once  saw  a  woman  who  (after  eating 
shell  fish)  vomited  so  violently  and  so  continuously  for 
about  a  week  that  she  died.  At  autopsy  the  only  thing  that 
could  be  found  was  a  small  patch  of  markedly  inflamed 
mucous  membrance  in  the  sigmoid  flexure.  Vomiting  can 
be  produced  by  irritating  or  distending  the  colon  with 
enemas.  Several  writers  (RoIIeston  and  Jex  Blake,376  Bine 
and  SchmoII60)  have  commented  on  the  vomiting  which 
not  infrequently  occurs  with  rectal  feeding.  The  more 
irritating  the  enema  is,  the  more  likely  it  is  to  cause  trouble. 
Several  of  my  patients  get  nausea  with  ordinary  injections 
of  water  or  normal  salt  solution,  but  they  vomit  when 
soap,  glycerine,  turpentine  or  glucose  is  added  to  the  solution. 
I  have  long  felt  that  the  Murphy  drip  is  responsible  for  some 
of  the  distress  and  nausea  suffered  by  people  after  abdominal 
operations,  and  my  experience  makes  me  feel  that  it  should 
be  used  only  when  necessary  to  replace  water  lost  by  bleed- 
ing and  vomiting.  Especially  after  operations  in  the  pelvis, 
nothing  should  be  put  into  the  rectum  which  will  tend  to 
raise  its  tone  still  farther  and  to  upset  the  gradient. 

CONSTIPATION.  There  are  good  reasons  for  believing 
that  normally  the  tone  of  the  rectum  and  sigmoid  is  higher 
than  that  of  the  cecum  or  of  the  ascending  colon  (Alvarez 


io6  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

and  Starkweather,17  Rost,378  p.  992).  This  tends  to  protect 
the  anal  sphincter  and  to  keep  feces  from  packing  into  the 
ampulla  excepting  during  those  times — as  after  breakfast 
— when  the  pressure  from  the  upper  part  of  the  tract  is  very 
great.  If  defecation  is  postponed,  it  can  occasionally  be  shown 
with  the  roentgen  ray  that  the  feces  have  returned  into  the 
sigmoid  or  even  into  the  descending  colon  (Schwartz,394 
Drummond,130  Kastle  andBruegel223;  personal  observations). 
The  commonest  cause  of  constipation  is  probably  an  increase 
in  the  tone  of  the  rectum  which  makes  the  gradient  steeper 
up  to  the  anal  ring  (Singer  and  Holzknecht401).  Any- 
thing which  keeps  up  an  irritation  in  the  lower  colon,  such 
as  hemorrhoids,  fissures,  fistulae,  or  a  diseased  ovary,  uterus 
or  prostate,  can  easily  bring  about  or  exaggerate  consti- 
pation. Ordinarily  constipation  seems  to  be  a  nervous 
disease;  the  stagnation  is  almost  always  in  the  rectum,  and 
the  increase  in  tone  of  the  sphincters  seems  to  be  a  part  of 
that  general  increase  in  tension  of  the  voluntary  muscles 
which  is  observed  so  commonly  in  constipated  people. 
The  writers  on  constipation  generally  classify  the  cases 
into  atonic  and  spastic.  In  the  first  type,  the  colon  is  sup- 
posed to  be  too  weak  to  force  onward  its  contents;  in  the 
second,  it  is  supposed  to  be  so  irritable  and  strong  that  it 
will  not  let  these  contents  go  by.  So  far  as  I  can  remember  I 
have  never  seen  an  atonic  case;  they  all  seem  to  be  spastic. 
The  believers  in  the  atonic  type  of  constipation  will  more- 
over find  it  hard  to  reconcile  their  views  with  the  obser- 
vations of  Miiller  and  Hesky,334  who  removed  all  the  muscle 
from  the  colons  of  dogs  and  found  that  it  produced  very 
little  disturbance  in  motility.  Apparently  the  muscle  of  the 
small  intestine  was  strong  enough  to  force  the  material 
onward  through  the  inactive  segment,  and  the  only  thing  to 
hold  it  back  was  the  muscle  around  the  anal  canal. 


APPLICATION  OF  THE  GRADIENT  IDEA         107 

DEPRESSION  AT  THE  LOWER  END.  So  far  we  know  very 
little  about  alterations  in  the  gradient  due  to  depression 
at  the  lower  end.  I  have  seen  some  cases  of  diarrhea  which 
seemed  to  me  to  be  due  almost  undoubtedly  to  the  loss  of 
tone  of  the  lower  end  of  the  bowel  following  extensive 
operations  for  fistula  in  ano.  In  these  cases,  every  stimulus 
from  above  produced  a  bowel  movement.  Normally,  such 
stimuli  probably  produce  a  surge  towards  the  rectum  which 
is  taken  up  or  thrown  back  by  the  tonic  state  of  the  lower 
bowel.  If  this  influence  is  removed  by  making  a  large  fistula 
into  the  lower  ileum,  the  food  will  go  through  the  small 
intestine  too  fast  (Demarquay,125  Macewen285).  It  is  sugges- 
tive that  in  most  cases  of  diarrhea  the  colon  is  atonic.  This 
can  be  seen  not  only  with  the  roentgen  ray  but 
it  shows  itself  also  in  the  ease  with  which  a  sigmoid- 
oscope  can  be  thrust  far  into  the  bowel.  On  the  other  hand, 
in  the  constipated,  the  anal  sphincters  and  sometimes  the 
whole  rectal  wall  are  exceedingly  tonic;  the  roentgen  ray 
shows  a  narrow  lumen  with  marked  haustration,  and  the 
sigmoidoscope  is  gripped  firmly.  A  serious  objection  can  be 
found  to  this  line  of  argument  in  the  work  of  Mliller  and 
Hesky,334  quoted  in  the  preceding  section.  Theoretically, 
the  removal  of  the  colonic  muscle  might  easily  cause  diar- 
rhea, but  according  to  these  investigators,  such  diarrhea  is 
transient  and  generally  gives  way  to  slight  constipation. 
The  problem  must  be  studied  further. 

AN  ILLUSTRATIVE  SIMILE.  Some  who  find  it  hard  to 
understand  what  a  gradient  of  forces  is  and  who  have  diffi- 
culty in  following  the  argument  as  I  have  outlined  it  in  the 
preceding  pages  may  be  helped  by  the  following  somewhat 
grotesque  simile: 

Let  us  imagine  a  game  of  push-ball  played  by  a  column  of 


io8.  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

men  who  have  been  graded  according  to  their  metabolic 
rates.  At  one  end  they  are  young,  wide  awake  and  active; 
at  the  other  end  they  are  old  and  comparatively  sluggish 
in  their  movements.  These  men  will  represent  the  muscle 
fibers  along  the  bowel.  The  first  young  man  takes  the  ball 
and  tries  to  push  it  past  the  second.  The  second  resists,  but 
is  soon  overcome  owing  to  the  greater  activity  and  aggres- 
siveness of  Number  i .  As  soon  as  the  ball  passes  Number  2  he 
joins  with  Number  i  in  trying  to  push  it  past  Numbers  3 
and  4.  Once  past  them,  Number  i  and  Number  2  rest  while 
Number  3  and  Number  4  push  it  past  Number  5  and  Number 
6;  and  so  it  goes.  The  men  in  the  first  third  of  the  line  (jeju- 
num) play  incessantly  so  long  as  the  ball  is  near  them,  and 
they  soon  force  it  down  among  the  old  men.  These  play  only 
at  intervals,  often  letting  the  ball  lie  quiet  while  they  rest. 
New  balls  are  sent  down  the  line  from  time  to  time  so  that 
the  old  men  generally  have  three  or  four  on  their  hands  at 
once.  They  are  aroused  to  get  rid  of  one  or  two  of  these  when 
they  see  that  a  new  one  has  started  down  (ileocolic  reflex 
and  defecation). 

Usually  the  ball  moves  in  one  direction  and  there  is  little 
likelihood  that  the  old  men  with  their  intermittent  efforts 
will  ever  overcome  the  youths,  but  one  day  some  of  the  old 
men  are  so  stimulated  by  some  drug  that  they  play  fast  and 
furiously,  and  the  others  cannot  push  the  ball  anywhere 
near  the  lower  goal.  On  another  occasion  some  of  the  old 
men  are  injured  and  this  stimulates  their  comrades  to  greater 
efforts  so  that  the  injured  ones  will  be  relieved  for  a  while 
from  the  trouble  of  handling  the  ball.  Their  efforts  may  be 
so  strenuous  that  the  balls  are  thrown  out  the  way  they 
entered.  On  still  another  occasion,  a  cloud  of  poison  gas  is 
liberated  over  the  players.  All  are  weakened  and  some 
become  ill,  but  the  young  men  who  breathe  faster  are  more 


APPLICATION  OF  THE  GRADIENT  IDEA         109 

susceptible  to  the  poison  and  suffer  more  from  the  lack  of 
proper  air  than  do  the  old  men.  Until  they  recover,  the  game 
is  slower,  but  the  old  men  are  now  relatively  more  active 
than  the  young  ones  and  the  ball  is  sometimes  sent  back 
to  its  original  starting  place. 

A  change  in  the  play  is  brought  about  also  when  the  balls 
are  made  unpleasant  or  painful  to  handle.  Perhaps  they  have 
been  filled  with  pepper  or  studded  with  sharp  spikes.  The 
first  one  or  two  to  start  down  the  line  are  rushed  through,  so 
that  the  players  can  get  rid  of  them  as  rapidly  as  possible. 
The  men  are  then  so  irritated  by  this  annoyance  that  they 
throw  back  the  next  few  balls  that  are  offered  them  (diarrhea 
and  vomiting). 

Some  physicians  at  first  confuse  the  gradient  of  forces 
with  the  gradient  of  gravity  due  to  the  position  of  loops 
of  bowel  in  the  abdomen.  Returning  to  the  simile,  it  will 
be  seen  that  if  the  game  of  push-ball  is  being  played  on  the 
side  of  a  hill  it  will  make  little  difference  whether  the  young 
men  are  above  or  below  the  old.  The  position  of  the  line  is 
not  the  important  thing  because  the  essential  factor  deter- 
mining the  movements  of  the  ball  is  the  gradient  of  activity 
and  strength  in  the  line  of  players.  Similarly,  physicians 
sometimes  think  that  because  there  is  stagnation  in  a  loop 
of  bowel  there  must  be  mechanical  obstruction  ahead  of  it. 
This  is  not  necessarily  the  case.  If  the  men  in  the  simile 
were  to  play  in  a  lane  between  two  board  fences,  a  slowing 
of  the  progress  of  the  ball  would  not  mean  necessarily  that 
the  lane  had  been  narrowed  or  closed.  As  likely  as  not 
some  of  the  players  might  be  fighting  -back  too  hard  or 
those  above  might  not  be  pushing  down  as  energetically 
as  usual. 

Some  may  be  surprised  at  the  idea  of  one  part  of  the 
bowel  resisting  the  propulsive  efforts  of  another  part  above, 


i  io  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

but  this  phenomenon  has  been  observed  by  so  many  people 
besides  myself  that  I  feel  no  doubt  about  it. 

DIETARY  SUGGESTIONS.  Some  may  ask:  In  what  way 
does  the  idea  of  a  gradient  altered  by  disease  influence  our 
methods  of  treatment?  The  answer  is  that  so  far  little  has 
been  done  because  therapeutists  have  not  been  thinking 
along  these  lines.  Later  we  may  be  able  to  get  drugs  which 
will  help  in  restoring  the  normal  gradient,  perhaps  as  calomel 
does  but  without  unpleasant  by-effects.  In  the  meantime 
there  is  a  diet  which  is  very  helpful,  probably  because  it  does 
not  lead  to  conflicts  with  disordered  gradients.  Years  ago  I 
became  impressed  with  the  fact  that  many  of  the  patients 
who  complained  of  flatulence  and  intestinal  unrest  were 
passing  stools  which  were  full  of  lumps  and  undigested 
material,  consisting  mainly  of  cellulose.  I  found,  also,  that  if 
I  could  remove  much  of  this  cellulose  from  their  diets  they 
would  often  get  great  relief;  and  the  digestion  of  starches,  as 
shown  by  the  stool  examination,  would  greatly  improve. 
It  seemed  to  me  then  that  the  virtues  of  the  smooth  diet 
were  to  be  ascribed  mainly  to  its  freedom  from  a  substance — 
cellulose — for  the  solution  of  which  the  body  has  no  ferment. 
In  recent  years  it  has  occurred  to  me  that  this  diet  might 
give  relief  to  the  digestive  tract  in  still  another  way.  Remem- 
bering the  experiment  described  in  Chapter  V  in  which 
reversed  segments  of  small  intestine  were  shown  to  transmit 
fluids  but  not  solids,  it  seemed  to  me  that  an  individual 
with  a  good  steep  gradient  might  be  able  to  handle  any 
amount  of  coarse  and  indigestible  material,  while  a  person 
with  a  poor  gradient  or  one  which  is  somewhat  upset  in 
places  would  be  unable  to  do  so.  Such  an  individual  should 
avoid  eating  coarse  food  for  much  the  same  reason  that  he 
should  avoid  putting  paper,  sticks  and  cotton  down  a  drain 


APPLICATION  OF  THE  GRADIENT  IDEA         in 

which  has  a  poor  drop  and  several  narrow  bends.  At  any 
rate,  whatever  the  reason,  this  diet  has  certainly  proved  in 
actual  practice  to  be  of  great  value  whenever  there  is  a 
slight  tendency  to  reverse  peristalsis  or  to  a  narrowing  of  the 
lumen  of  the  bowel.  Thus  it  is  useful  postoperatively  when 
suture  lines  or  segments  of  bowel  are  still  irritable;  and  it  is 
absolutely  essential  in  mild  intestinal  obstruction,  as  with 
carcinoma  of  the  bowel. 

The  following  is  the  list  which   I  give  to  my  patients: 

SMOOTH  DIET  LIST 

Choose  from  the  following: 

Breakfast 

Orange  juice;  grape  fruit  (avoid  the  fiber). 

Cantaloupe  and  melons  are  inadvisable  as  they  tend  to  regurgi- 
tate for  hours. 

Coffee  in  moderation;  chocolate;  cocoa  or  tea. 

One  or  two  eggs  with  ham  or  bacon  (avoid  the  purely  fibrous 
part). 

White  bread  and  butter;  toast  or  zwiebach. 

Any  smooth  mush,  such  as  farina;  germea;  cream  of  wheat; 
cornmeal  or  strained  rolled  oats. 

Puffed  cereals  and  corn  flakes  are  also  allowed. 

Shredded  wheat  biscuits  and  other  coarse  breakfast  foods  are 
not  allowed. 

Lunch  or  Dinner 

Broths;  bouillon;  cream  soups;  chowder. 

Small  portion  of  meat,  fish,  oysters,  chicken  or  squab  (avoid 
the  fibrous  parts  and  gristle). 

No  smoked  or  canned  fishes,  or  pork. 

Avoid  veal,  crab  and  lobster  if  they  seem  to  cause  indigestion. 


ii2  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

White  bread  and  butter;  hot  biscuits  made  small  so  as  to  con- 
sist mainly  of  crust.  No  rough  branny  breads  or  bran  biscuits. 

Rice;  potatoes — baked,  mashed,  hashed-brown  or  French-fried; 
sweet  potatoes;  hominy;  tomatoes  stewed,  strained  and  with 
cracker  crumbs;  well  cooked  cauliflower^tops  with  cream  sauce; 
and  asparagus  tips.  Later  may  try  brussels  sprouts.  Italian 
pastes;  noodles,  macaroni  or  spaghetti,  cooked  soft  with  a  little 
cheese  or  cream  sauce. 

Purees  of  peas;  beans;  lentils;  lima  beans  or  artichoke  hearts. 
All  skins  or  fiber  should  be  removed  by  passing  through  a  ricer. 
"Cornlet"  in  cans  furnishes  sweet  corn  without  the  indigestible 
husks.  There  are  practically  no  other  vegetables  that  can  be 
pureed  to  advantage.  Spinach  often  causes  trouble  and  is  not 
recommended.  Bananas  can  be  fried  in  butter  or  baked  in  their 
skins.  String  beans  are  allowed  if  young  and  tender.  No  salads 
at  first.  Later  you  may  try  a  little  tender  lettuce  with  apples  or 
bananas,  tomato  jelly  or  boiled  egg.  Mayonnaise  and  French 
dressing  are  allowed. 

For  Dessert 

Simple  puddings,  custards,  ice-cream,  jello,  plain  cake,  canned 
or  stewed  fruit.  Avoid  cheese,  nuts  and  raisins. 

If  constipated,  stewed  fruit  may  be  taken  once  or  twice 
a  day.  In  winter,  the  dried  pared  fruit  may  be  used  for  stew- 
ing. Too  much  sugar  should  not  be  added.  Apple  sauce 
is  much  more  palatable  if  made  from  unpared  and  uncored 
apples.  The  sauce  is  strained  later.  It  may  be  diluted 
with  a  little  tapioca  or  sago.  The  apples  may  be  baked. 
Blackberries  and  loganberries  can  be  stewed  and  strained, 
and  the  sweetened  juice  thickened  with  cornstarch.  This 
makes  a  delicious  dish  with  the  full  flavor  of  the  berries. 
Canned  fruits,  such  as  pears  and  peaches,  are  allowed. 
Later  you  may  try  a  fully  ripe  pear,  peach  or  apple. 

Avoid  most  of  the  green  vegetables,  salads  and  raw  fruits. 


APPLICATION  OF  THE  GRADIENT  IDEA         113 

Avoid  sugar  in  concentrated  form;  take  no  candy  or  other 
food  between  meals. 

Avoid  eating  in  a  rush  or  when  mentally  distraught. 

Objections  may  be  made  that  such  a  diet  will  lead 
promptly  to  constipation,  but  practically  it  has  rarely 
done  so,  and  in  a  number  of  cases  it  has  actually  relieved 
constipation. 


CHAPTER  X 
REVERSE  PERISTALSIS  AND  ITS  SYMPTOMS 

IT  can  easily  be  shown  that  most  of  the  symptoms  of 
gastro-intestinal  disease  are  due  to  disturbances  in  the 
mechanical  functions.  Thus,  the  great  obstacle  to  the 
making  of  an  early  diagnosis  of  cancer  of  the  stomach  is  the 
fact  that  the  mucous  membrane  and  the  gastric  secretion 
may  be  almost  entirely  gone  and  yet  the  patient  may  have  no 
symptoms.  These  arise  only  when  the  growth  becomes  large 
enough  to  block  the  pylorus,  and  even  after  that,  they  may 
disappear  entirely  when  a  channel  sloughs  through  the  tumor. 
As  Taylor423  has  aptly  said,  we  seem  to  have  duplicate  plants 
for  chemical  digestion,  but  we  have  only  one  muscular  tube 
for  the  motor  transport  of  food.  Naturally,  when  that  breaks 
down  we  are  very  promptly  apprised  of  the  fact.  As  we 
undoubtedly  get  symptoms  when  the  transport  is  slowed  or 
stopped,  it  seems  to  me  that  we  must  get  them  also  when 
it  is  reversed.  I  might  add  that  we  get  very  definite  sensa- 
tions from  the  bowel  also  when  the  transport  is  speeded. 
In  a  sensitive  person  the  peristaltic  rushes  which  usher  in 
an  attack  of  diarrhea  may  be  very  distressing.  They  produce 
a  peculiar  sinking  feeling  in  the  epigastrium  which  may 
be  accompanied  by  chills,  cold  sweats,  pallor  of  the  skin 
and  even  fainting. 

Now  it  has  been  shown  in  the  preceding  chapter  that  the 
reverse  transport  of  food  in  the  tract  is  not  uncommon. 
In  some  places  it  is  physiologic.  We  know  that  the  duodenal 
contents  regurgitate  into  the  stomach.  We  know  that  there 

114 


REVERSE  PERISTALSIS  115 

is  reverse  peristalsis  in  the  upper  half  ot  the  colon;  and  all 
of  us  are  acquainted  with  the  phenomena  of  belching, 
regurgitation  and  vomiting.  Since  the  time  of  Hippocrates, 
physicians  have  commented  upon  the  fecal  vomiting  of 
ileus;  and  there  are  innumerable  well  authenticated  in- 
stances in  which  people  have  vomited  enemas  and  supposi- 
tories (Schloffer,388  Langmann,251  Weber441).  A  review  of 
the  literature  shows  a  surprising  number  of  cases  in  which 
these  observations  caused  surgeons  to  operate  for  a  gastro- 
colic  fistula  which  was  not  found  (Treves433).  I  have  talked 
with  a  number  of  intelligent  persons  who  objected  to  their 
nutrient  enemas  because  they  were  regurgitating  some  of 
the  material,  and  did  not  like  its  bitter  taste.  Doctor  Emge 
of  San  Francisco  tells  me  that  after  severe  pelvic  operations 
it  is  his  custom  to  give  enemas  of  coffee  which  not  infre- 
quently can  be  detected  in  the  vomited  material.  At  first 
he  thought  it  was  dark  blood,  but  a  chemical  examination 
showed  that  it  was  coffee. 

It  is  well  known  that  in  most  instances  barium  enemas 
flow  back  into  the  ileum  and  that  occasionally  the  material 
will  reach  the  duodenum  (Quimby,367  p.  403).  I  have  seen 
liquid  and  gas  pass  rapidly  from  the  colon  to  the  duodenum 
in  cats.  The  animals  were  anesthetized  and  their  abdomens 
opened  under  salt  solution.  The  rectum  was  tied  off  and  the 
colon  filled  with  air  or  thick  soup.  After  that  part  of  the 
bowel  had  become  very  irritable  and  highly  tonic  through  its 
efforts  at  emptying,  some  of  the  material  was  rushed  well 
up  into  the  small  intestine. 

Granting,  then,  that  the  possibility  of  reverse  transport 
of  food  through  the  tract  is  well  established,  the  next  question 
is:  Are  there  mild  forms  in  which  perhaps  the  gradient 
is  simply  flattened,  or  in  which  there  are  ripples  travelling 
up  the  bowel,  and  do  these  ripples  cause  symptoms? 


ii6  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

Do  they  affect  the  consciousness  of  the  individual  and  if  so, 
how?  In  the  following  paragraphs  I  wish  to  discuss  a  few 
symptoms  which  are  often  found  together  or  alternating 
one  with  the  other  in  the  same  patient,  and  which  I  believe 
indicate  such  mild  reverse  peristalsis.  These  symptoms  are 
vomiting,  regurgitation,  heart-burn,  belching,  nausea, 
socalled  biliousness,  coated  tongue,  some  types  of  foul 
breath,  a  feeling  of  fulness  immediately  after  beginning 
a  meal,  globus  and  possibly  at  times,  hiccup  (Alvarez9). 
In  taking  a  history,  these  symptoms  should  be  inquired 
into  very  carefully  because  if  the  patient  has  a  lesion 
anywhere  along  his  tract  sufficiently  irritable  to  alter  the 
gradient,  he  should  have  some  of  these  manifestations. 
If,  on  the  other  hand,  he  complains  only  of  a  little  flatulence 
with  some  discomfort  or  vague  pain  one  must  be  slow  to 
make  the  diagnosis  of  an  organic  lesion. 

(i)  VOMITING.  The  act  of  vomiting  is  accomplished  with 
the  help  of  a  center  in  the  medulla  which  coordinates  the 
movements  of  the  voluntary  muscles  with  those  of  the 
digestive  tract.  Unfortunately,  so  many  even  of  the  physi- 
ologists have  been  obsessed  with  the  idea  that  the  stomach 
is  the  organ  of  digestion  that  very  few  of  them  have  paid 
any  attention  to  the  behavior  of  the  intestine  during  vomiting. 
I  believe  that  a  little  more  careful  observation  would  show 
that  in  many  cases  the  bowel  does  play  a  considerable  part, 
perhaps  not  so  much  in  the  act  of  vomiting  itself,  but  in 
the  preparation  for  it.  Thus,  on  some  occasions,  while 
watching  the  contractons  of  the  intestine  in  animals  opened 
under  salt  solution,  I  was  struck  by  the  fact  that  violent 
contractions  in  the  jejunum  were  followed  a  few  seconds 
later  by  the  regurgitation  of  material  through  the  mouth. 
I  have  graphic  records  from  the  intestines  of  cats,  and  also 


REVERSE  PERISTALSIS  117 

from  a  man  with  a  jejunal  fistula,  showing  that  a  marked 
rise  in  the  tone  of  the  upper  bowel  preceded  vomiting.  Less 
convincing  observations  were  made  on  a  child  with  severe 
recurrent  vomiting,  in  whom  the  attacks  were  preceded  by 
violent  intestinal  peristalsis  and  borborygmus  loud  enough 
to  be  heard  several  feet  away. 

A  review  of  the  literature  shows  that  a  few  writers  have 
made  similar  observations.  Openchowski,345  in  describing 
vomiting,  speaks  of  a  preliminary  increase  in  the  activity 
of  the  bowel;  and  Boldireff63  (p.  489),  one  of  the  best  of  the 
Russian  observers,  noticed  during  some  experiments  that 
periods  of  intestinal  activity  were  sometimes  accompanied 
by  vomiting.  Such  activity  tends  to  force  intestinal  contents 
back  into  the  stomach.  I  have  been  able  to  confirm  EwakTs144 
statement  that  in  ileus  the  stomach  is  filled  with  such 
regurgitated  material  for  some  time  before  fecal  vomiting 
appears.  If  long  stretches  of  bowel  are  operatively  reversed 
in  dogs  so  that  the  current  is  directed  backward  towards  the 
stomach,  the  animals  will  vomit  unless  fed  very  care- 
fully (Kelling,233  p.  326).  Von  Bechterew  and  Weinberg43 
(p.  259)  say  that  curarized  animals  which  cannot  vomit 
will  regurgitate  when  given  certain  emetics. 

Physicians  seem  to  think  sometimes,  because  they  find 
so  much  bile  in  the  vomitus,  that  it  is  producing  the  emesis. 
It  has  been  well  proved  that  that  is  not  so,  because  the 
duodenum  has  been  closed  off  in  dogs  and  in  man  so  that  all 
the  secretions  of  the  liver  and  pancreas  had  to  go  through 
the  stomach  on  their  way  into  the  jejunum  (through  a  gastro- 
enterostomy)  and  yet  there  was  no  vomiting  (Chlumski,114 
Rosenberg,377  Ledderhose,257  Moynihan,329  Kolbing,239 
Wiedemann446).  Hence  it  seems  to  me  that  when,  as 
commonly  happens,  we  find  large  amounts  of  bile-stained 
fluid  in  a  stomach  which  has  been  emptied  a  few  minutes 


n8  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

before,  we  can  be  sure  that  it  has  come  from  the  bowel, 
and  that  the  same  cause  which  is  producing  the  back-flow 
is  producing  the  vomiting. 

Physicians  often  think  that  they  can  stop  vomiting  if 
only  they  can  keep  food  out  of  the  stomach.  They  forget  that 
vomiting  is  often  very  severe  with  lesions  far  down  in  the 
bowel  and  that  it  may  be  entirely  lacking  in  serious  gastric 
disease,  such  as  ulcer  and  carcinoma,  without  pronounced 
pyloric  obstruction  (Faulhaber  and  von  Redwitz,148  p.  680). 
Cohnheim  and  Dreyfus117  (p.  56)  produced  vomiting  in 
dogs  by  distending  balloons  in  the  intestine.  They  found 
that  a  slowing  of  gastric  emptying  could  easily  be  effected 
by  irritating  the  bowel,  whereas  it  was  not  observed  after 
the  production  of  a  severe  gastritis.  Hirsch189  (p.  380)  pro- 
duced vomiting  in  dogs  by  giving  solutions  of  organic  acids. 
Acetic  acid  was  most  effective,  apparently  because  it  had  the 
least  action  on  the  stomach  and  the  most  marked  stimulating 
effect  on  the  intestine.  The  regurgitation  of  bile-stained 
contents  into  the  stomach  showed  that  the  gradient  was 
upset.  Lactic  acid,  which  had  less  effect  on  the  gradient, 
produced  only  a  delay  in  gastric  emptying. 

As  is  well  known,  vomiting  is  often  observed  in  preg- 
nancy, particularly  during  the  first  few  months.  Obstetricians 
generally  distinguish  between  the  milder  cases  in  which 
the  cause  is  said  to  be  "reflex/*  and  the  severer  ones  in 
which  the  cause  is  probably  a  toxemia.  I  have  been  impressed 
by  the  fact  that  nausea  and  vomiting  very  similar  to  that  in 
pregnancy  is  observed  in  women  whose  pelvic  organs  are 
kept  irritated,  inflamed  or  abnormally  hyperemic  by  unsatis- 
factory suspension  operations;  by  fibroids,  pus-tubes  or 
diseased  ovaries.  These  lesions  keep  the  uterus  in  much  the 
same  condition  as  it  is  in  the  first  few  months  of  pregnancy; 
and  the  symptoms  disappear  immediately  after  the  oper- 


REVERSE  PERISTALSIS  119 

ative  removal  of  the  source  of  irritation.  It  has  occurred  to 
me  that  the  increased  activity  and  vascularization  of  the 
uterus  in  pregnancy  and  with  these  inflammations  might 
in  some  way  raise  the  tone  and  irritability  of  the  lower  part 
of  the  bowel,  and  thus  reverse  the  gradient.  So  far  I  have 
been  able  to  study  the  gradient  in  only  a  few  pregnant 
animals.  In  most  of  these  there  was  little  change  shown  in 
the  rhythmicity  of  the  excised  segments;  and  it  is  only 
suggestive  that  in  a  few  animals  studied  with  the  abdomen 
open  under  salt  solution  the  rhythmic  gradient  was  markedly 
flattened  by  an  increase  in  the  rate  of  the  ileum.  That  the 
gradient  in  pregnant  women  is  flattened  is  suggested  not 
only  by  the  vomiting  but  by  the  regurgitation  of  acid 
gastric  contents  into  the  mouth.  Some  women  will  suffer 
during  one  pregnancy  from  vomiting  and  during  another 
from  severe  heart-burn. 

It  is  possible  that  the  lower  bowel  shares  in  the  hyperemia 
of  the  pelvic  organs.  There  may  also  be  a  spread  of  "tone" 
along  the  pelvic  nerves.  Elliott  and  Barclay  Smith138  (p. 
282)  found  that  stimulation  of  these  nerves  will  raise  the 
tone  of  the  midregion  of  the  colon  and  will  increase  the 
tendency  to  reverse  peristalsis  there.  Quite  a  few  women 
notice  a  tendency  to  diarrhea  on  the  first  day  of  menstrua- 
tion, and  there  again  we  have  evidence  of  some  effect 
transmitted  from  the  hyperemic  uterus  to  the  bowel.  The 
fact  that  a  uterine  hyperemia  from  any  cause  may  upset  the 
intestinal  gradient  makes  me  feel  that  the  action  in 
pregnancy  must  often  be  direct  and  not  by  way  of  any 
toxemia. 

The  tendency  to  reverse  peristalsis  in  pregnancy  was  well 
recognized  years  ago  by  Campbell.79  He  states  clearly  that 
the  woman  with  pregnancy  or  pelvic  disease  has  an  irritable 
tract  in  which  "response  is  usually  by  inverted  rather  than 


120  THE  MECHANICS  OF  THE- DIGESTIVE  TRACT 

by  direct  action :  eructation,  regurgitation,  nausea,  vomiting, 
constipation,  far  more  frequently  than  diarrhea  and  other 
manifestations  of  downward  action.  The  tract  gets  into  the 
habit  of  retrostalsis."  The  stormy  vomiting  and  dynamic 
ileus  seen  sometimes  after  pelvic  operations  may  be  due  to  a 
great  and  sudden  increase  in  the  irritability  of  the  colon. 
One  may  perhaps  explain  also  in  this  way  the  vomiting 
seen  sometimes  after  injury  to  the  testicle  (Mliller,336 
P-  37)-  Upsets  in  digestion  may  be  produced  also  in  men  by 
enlarged  prostates  and  distended  bladders  (Peyer,359  p. 
3182;  Herschell,186  Hutchison,206  p.  485;  Stockton,413  p.  129; 
Austin,26  p.  52).  These  seem  to  correspond  closely  with  those 
observed  in  women  with  inflamed  and  gravid  pelvic  organs. 
Many  will  say  that  these  things  are  purely  "reflex,"  but 
that  word  does  not  help  us  very  much;  and  I  think  we  are 
justified  in  looking  for  a  simpler  and  better  explanation. 
Vomiting  can  sometimes  be  stopped  by  giving  solid  food 
which  may  act  perhaps  by  raising  the  tone  of  the  stomach 
and  restoring  the  downward  gradient.  Liquids  often  fail  to 
stop  vomiting,  perhaps  because  they  tend  to  run  directly 
into  the  intestine  without  affecting  the  stomach  very  much. 

(2)  REGURGITATION.  In  true  vomiting,  the  return  of  the 
gastric  contents  into  the  mouth  is  effected  mainly  by  con- 
tractions of  the  voluntary  muscles  in  the  abdomen  and 
thorax;  in  regurgitation,  it  is  effected  mainly  or  solely  by 
contractions  in  the  smooth  muscle  of  the  stomach,  bowel 
and  esophagus.  There  are,  however,  many  grades  or  stages 
between  the  two — between  the  projectile  vomiting  in  cases 
of  brain  tumor,  and  the  half  vomiting,  half  regurgitation 
often  seen  in  infants  and  in  hysterical  girls.  Furthermore, 
a  woman  with,  let  us  say,  an  irritable  gall-bladder  may 
regurgitate  during  some  of  her  attacks  and  vomit  in  others. 


REVERSE  PERISTALSIS  121 

Regurgitation  is  commonly  observed  even  in  people  with 
good  digestions,  if  they  eat  certain  foods  like  onions,  musk- 
melons,  bananas  or  fats.  They  can  taste  these  foods  at  inter- 
vals for  hours  after  they  are  eaten.  The  fats  probably  act  in 
this  way  because  while  they  depress  the  gastric  activity  (von 
Tabora,420  Cannon,83  p.  315),  they  stimulate  that  of  the 
bowel,  and  thus  increase  the  normal  tendency  to  duodenal 
regurgitation  (Babkin,28  Lintwarew269).  It  has  often  struck 
me  as  suggestive  that  those  foods  which  cause  regurgitation 
when  eaten  in  small  amounts  may  cause  vomiting  when 
eaten  in  large  amounts.  Furthermore,  some  of  them  produce 
heart-burn  in  some  people;  and  we  shall  see  later  that  that 
is  due  probably  to  the  regurgitation  of  the  gastric  juice  into 
the  pharynx. 

Some  women  regurgitate  at  the  beginning  of  the  menstrual 
period;  others  have  a  great  deal  of  trouble  with  it  during 
pregnancy.  The  fact  that  troublesome  regurgitation  may 
cease  a  few  minutes  after  the  patient  has  a  bowel  movement 
suggests  strongly  that  the  distension  of  the  pelvic  colon  can 
keep  that  region  overactive  and  can  cause  it  to  give  off 
reverse  waves.  These  waves  need  not  be  so  powerful  that 
they  sweep  material  along  before  them.  I  have  commented 
elsewhere  on  the  fact  that  in  the  rabbit's  intestine  peristaltic 
rushes  here  and  there  can  be  shown  by  graphic  records  to 
have  originated  in  ripples  which  have  come,  unnoticed  by 
the  naked  eye,  all  the  way  from  the  pylorus  (Alvarez3). 
It  seems  to  me  probable  that  ripples  coming  from  a  full 
or  overactive  colon,  or  from  the  irritable  ileocecal  region  in 
subacute  appendicitis  can  run  up  the  bowel  and  show  them- 
selves in  the  stomach  and  esophagus  as  waves  of  acid  regur- 
gitation. Smith  and  Lewald403  (p.  271)  have  commented 
upon  the  frequency  with  which  regurgitation  accompanies 
colic  in  children.  It  is  probable  that  the  waves  causing  this 


122  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

regurgitation  arise  in  the  overactive  part  of  the  bowel.  The 
following  case  is  very  suggestive:  A  constipated  infant 
regurgitated  so  much  every  day  that  her  pillow  was  always 
soaked.  After  weeks  of  this  her  bowels  suddenly  became  a 
little  loose;  and  the  day  on  which  this  occurred  the  mother 
was  surprised  to  find  the  pillow  perfectly  dry.  It  remained 
that  way  for  over  a  week  until  the  bowels  became  constipated 
again.  Apparently  the  establishment  of  a  good  current  down- 
ward instantly  stopped  all  regurgitation  upward.  Hippo- 
crates seems  to  have  had  very  similar  ideas  about  the 
gradient,  because  he  says:  "In  confirmed  diarrhea,  vomiting, 
when  it  comes  on  spontaneously,  removes  the  diarrhea188." 
I  have  seen  exactly  that  thing  happen  in  cases  of  tuberculosis 
of  the  cecum. 

(3)  HEART-BURN.  Before  giving  my  views  as  to  what 
heart-burn  is  I  must  emphasize  what  it  is  not.  Practically 
every  one  who  has  studied  the  subject  has  agreed  that  only 
a  small  proportion  of  the  patients  complaining  of  sour 
stomach  or  heart-burn  have  an  actual  increase  in  their 
gastric  acidity  (Schiitz,393  Steele,409  Stockton,413  p.  157), 
Titration  of  the  burning  fluid  that  has  been  regurgitated 
often  shows  subacidity;  and  gastric  analyses  made  during 
the  periods  of  discomfort  do  not  show  values  any  higher 
than  those  found  during  periods  of  relief.  Furthermore,  all 
of  those  who  have  put  from  0.5  to  2.0  per  cent  hydrochloric 
acid  by  tube  into  the  human  stomach  agree  that  their 
subjects  could  hardly  perceive  it  (Hurst,200  p.  101;  Ginsburg, 
Tumpowsky  and  Hamburger,166  Carlson  and  Braafladt,97 
p.  163;  Zimmermann,455  Lowenthal,274  Schiir,392  Schmidt389). 
At  most  there  is  a  slight  sensation  of  warmth.  A  number  of 
writers  have  felt  that  they  could  explain  away  the  difficulty 
by  saying  that  the  diseased  stomach  is  so  hyperesthetic  that 


REVERSE  PERISTALSIS  123 

it  can  feel  the  acid.  This  idea  has  been  discredited  by  the 
work  of  Hurst201  (p.  12),  Lowenthal,274  and  Schiir,392  who 
showed  that  persons  with  ulcer,  demonstrated  later  at 
operation,  could  not  feel  the  acid  any  more  than  normal 
persons  can.  Other  explanations  for  the  appearance  of  heart- 
burn have  been  offered,  but  it  seems  to  me  the  true  one  is 
that  given  by  Reichmann,374  thirty-seven  years  ago.  He  had 
people  swallow  a  little  gelatin-coated  sponge  on  the  end  of  a 
string.  After  leaving  it  for  ten  minutes  in  the  lower  eso- 
phagus, he  pulled  it  out,  squeezed  it,  and  found  that  the 
fluid  expressed  was  acid  in  the  persons  who  had  heart-burn, 
and  alkaline  in  normal  controls.  He  concluded,  therefore, 
that  heartburn  was  due  to  a  regurgitation  of  gastric  juice. 
This  view  has  been  held  independently  by  a  number  of  men, 
but  some  doubt  has  been  cast  upon  it  by  the  work  of  Hurst,201 
(p.  12)  who  states  that  the  esophagus  is  not  sensitive  to  acid. 
This  is  not  true  for  all  people.  Those  who  have  prescribed 
hydrochloric  acid  in  cases  of  achylia  gastrica  know  that 
some  people  complain  of  its  burning  them  and  others  do  not. 
I  have  experienced  severe  and  typical  heart-burn  after 
drinking  a  solution  of  acidol,  a  drug  which  liberates  hydro- 
chloric acid  when  dissolved  in  water.  The  lower  pharynx 
is  probably  more  sensitive  to  the  acid  than  is  the  rest  of  the 
esophagus,  and  many  people  say  they  feel  the  heart-burn 
in  the  back  of  the  throat.  One  cannot  be  sure  about  that 
localization,  however,  because  it  is  known  that  sensations 
derived  from  the  esophagus  between  the  clavicle  and  nipple 
may  be  referred  either  upward  into  the  throat  or  downward 
into  the  epigastrium  (Boring,65  p.  34).  Some  intelligent 
people  who  have  suffered  greatly  from  heart-burn  have  told 
me  that  their  dentists  have  found  that  the  enamel  was  badly 
eaten  off  of  their  back  teeth;  and  I  believe  some  one  has 
suggested  that  regurgitation  of  acid  juice  may  be  one  of  the 


i24   THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

causes  for  that  deterioration  of  the  teeth  which  is  so  often 
seen  in  pregnant  women. 

Some  nervous  women  complain  at  times  of  a  burning 
feeling  in  the  epigastrium,  as  if  the  stomach  were  "on  fire." 
This  seems  to  be  an  entirely  different  thing.  The  fact  that 
it  sometimes  moves  to  the  lower  part  of  the  abdomen  or 
down  on  to  the  thigh  shows  that  it  is  a  paresthesia  which  has 
nothing  to  do  with  the  stomach. 

One  of  the  most  suggestive  things  about  true  heart-burn 
is  its  well  known  association  with  belching  and  regurgitation. 
Many  say  that  they  feel  the  burning  only  when  the  fluid 
comes  up.  Occasionally  it  is  worse  when  they  are  lying  down, 
perhaps  because  the  gastric  juice  can  then  more  easily  run 
back  up  the  esophagus.  It  is  often  brought  on  by  eating  fats 
which,  as  is  well  known,  tend  to  regurgitate.  Some  men  suffer 
from  heart-burn  after  using  tobacco.  Perhaps  in  the  habitue, 
regurgitation  of  gastric  juice  takes  the  place  of  the  nausea 
and  vomiting  of  the  neophyte.  Similarly,  in  a  few  sensitive 
individuals  small  doses  of  digitalis  cause  heart-burn  whereas, 
as  is  well  known,  in  large  doses  it  produces  vomiting. 

If  people  with  heart-burn  ordinarily  have  no  increase  of 
gastric  acidity,  why  are  they  so  often  relieved  temporarily 
by  the  taking  of  alkalies?  It  seems  to  me  that  this  may  do 
good  .in  several  ways:  First,  by  neutralizing  the  acid  in  the 
stomach;  secondly,  by  enabling  the  person  to  belch  so 
noisily  and  satisfactorily  that  he  does  not  feel  like  doing  it 
again  for  some  time;  and  thirdly,  perhaps,  by  quieting  the 
contractions  of  the  stomach. 

If  heart-burn  is  due  to  regurgitation  of  gastric  contents 
into  the  esophagus,  why  is  it  that  the  fluid  that  comes  up 
sometimes  tastes  fresh  and  sweet  while  at  other  times,  in  the 
same  person,  it  is  intensely  acid  and  bitter?  It  is  now  well 
known  that  there  are  three  parts  of  the  stomach:  (i)  the 


REVERSE  PERISTALSIS  125 

fundus,  which  holds  the  food  fairly  motionless,  often  in 
layers  as  it  comes  in;  (2)  the  muscular  antrum,  which  breaks 
the  food  up  and  mixes  it  with  the  gastric  juice;  and  (3)  the 
canalis  gastricus  which  carries  fluids  along  the  lesser  curva- 
ture and  out  into  the  duodenum.  It  seems  to  me  that  the 
regurgitated  food  that  tastes  fresh  has  probably  come  from 
the  top  of  the  pile  in  the  fundus,  the  burning  liquid  has  come 
from  the  antrum  or  even  from  the  duodenum,  and  has 
probably  travelled  up  the  gastric  canal.  Schilling387  found 
that  the  regurgitated  fluid  was  alkaline  in  some  people,  and 
in  one  case  he  though  it  was  pure  duodenal  juice. 

Heart-burn  is  often  very  severe  and  trying  in  pregnancy 
where  it  may  take  the  place  of  vomiting.  Some  women  will 
have  vomiting  with  one  pregnancy  and  severe  heart-burn 
with  another.  It  is  present  sometimes  on  the  first  day  of 
menstruation.  It  may  be  a  pronounced  symptom  with  certain 
pelvic  diseases  and  also  at  the  menopause.  In  many  of  the 
older  women,  however,  it  must  be  admitted  that  the  reverse 
waves  may  be  arising  in  a  diseased  gall-bladder.  Heart- 
burn is  often  a  marked  symptom  in  chronic  appendicitis,  in 
duodenal  ulcer,  and  in  gall-bladder  disease.  In  all  of  these 
conditions  I  think  it  represents  reverse  peristalsis  arising 
near  the  lesion. 

(4)  BELCHING.  We  may  first  distinguish  three  types:  (i) 
a  gurgling  sensation  or  sound  which  seems  to  run  up  the 
esophagus,  and  perhaps  out  along  the  eustachian  tubes; 

(2)  involuntary  regurgitation  of  gas  from  the  stomach;  and 

(3)  a  voluntary  swallowing  and  expulsion  of  air.  This  air 
ordinarily  descends  only  into  the  middle  or  lower  esophagus, 
but   occasionally   some   of  it   is   forced   into  the   stomach 
(Kantor225).  I  often  tell  these  people  that  they  are  simply 
scratching  themselves  with  the  air.  Often,  as  with  scratch- 


126  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

ing,  the  more  the  victim  does  the  more  he  wants  to  do,  so 
that  the  quickest  way  in  which  to  get  relief  is  to  desist  until 
the  desire  has  passed  off. 

Although  many  of  these  patients  are  neurotic  and  are 
suffering  from  a  bad  habit,  I  believe  that  many  of  them 
actually  have  some  organic  lesion  which  is  sending  off 
reverse  waves,  is  making  them  uncomfortable,  and  is  giving 
them  the  desire  to  belch.  It  is  remarkable  the  amount  of 
relief  that  they  get  sometimes  by  taking  a  little  sodium 
bicarbonate.  A  man  will  wake  up  about  two  in  the  morning 
with  great  distress;  for  an  hour  he  may  walk  the  floor, 
rubbing  his  abdomen  and  trying  to  belch.  Finally,  after 
taking  some  soda,  he  belches  noisily;  perhaps  he  vomits 
a  little  bile  and  water,  and  within  a  few  minutes  he  is 
comfortable  and  falls  asleep.  The  relief  obtained  is  so  out 
of  proportion  to  the  amount  of  air  or  liquid  expelled  that  it 
seems  to  me  that  it  must  be  due  to  a  quieting  down  of  the 
tract  after  the  reverse  waves  have  succeeded  in  running 
out.  I  can  only  compare  it  to  the  tremendous  mental  and 
physical  relief  that  comes  to  a  sensitive  person  when  he 
reaches  the  toilet  after  he  has  restrained  a  rectum  full  of 
gas  for  hours  at  some  public  gathering.  The  violent  per- 
istaltic contractions  cease  instantly  and  the  whole  nervous 
system  quiets  down. 

(5)  NAUSEA.  It  is  well  known  that  nausea  ordinarily 
precedes  or  accompanies  vomiting.  It  seems  to  me  very 
probable  that  it  is  brought  about  by  reverse  peristalsis, 
particularly  in  the  bowel.  It  apparently  is  not  produced  by 
lesions  of  the  stomach  alone  because  it  is  often  entirely 
absent  with  extensive  carcinomas  of  the  organ,  and  it  is 
not  a  prominent  symptom  of  gastric  ulcer.  It  is  much  more 
common  in  acute  and  subacute  appendicitis  and  in  other 


REVERSE  PERISTALSIS  127 

inflammations  of  the  lower  bowel.  As  is  well  known,  it  is 
very  severe  in  pregnancy  and  in  other  disturbances  of  the 
pelvic  organs.  It  is  often  marked  in  hysterical  women  who 
show  other  signs  of  reverse  peristalsis.  More  rarely,  it  is 
observed  in  men  with  large  prostates  and  distended  bladders. 
I  have  seen  it  as  the  first  and  for  months  the  only  symptoms 
of  carcinoma  of  the  colon  but  I  have  never  seen  it  with  eso- 
phageal  disease  or  with  regurgitation  due  to  cardiospasm. 
Dogs  appear  to  be  nauseated  when  irritant  solutions  are 
injected  through  fistulae  into  their  upper  bowels;  and  we 
know  that  these  substances  regurgitate  into  the  stomach 
(Cohnheim  and  Dreyfus,117  p.  2484). 

Patients  suffering  from  nausea  sometimes  describe  it  as 
coming  in  ascending  waves,  and  I  have  noticed  the  same 
thing  myself.  It  has  made  me  wonder  if  possibly  I  was 
feeling  actual  reverse  waves  in  the  bowel.  When  I  am 
nauseated,  the  distress  is  lessened  by  lying  on  the  right  side 
and  is  made  much  worse  by  lying  on  the  left.  Other  people 
have  told  me  the  same  thing;  but  some  think  their  nausea 
is  worse  when  they  lie  on  the  right.  These  observations 
suggest  that  the  sensation  is  affected  by  the  position  of  the 
gastric  contents.  Nausea  may  be  produced  also  by  pulling 
on  the  mesentery  during  abdominal  operations  under  local 
anesthesia  (Farr147).  Barclay,31  believes  that  nausea  is  asso- 
ciated in  man  with  a  drop  in  gastric  tone. 

The  nausea  caused  by  disgusting  mental  impressions; 
by  rolling  movements,  as  at  sea  and  by  cerebral  and  aural 
disease,  might  conceivably  be  due  to  a  reversal  of  the 
gradient  in  the  upper  part  of  the  tract,  brought  about  by 
an  unequal  or  dissimilar  action  of  the  vagus  on  different 
parts  of  the  stomach  and  bowel.  This  possibility  has  been 
discussed  in  the  preceding  chapter.  It  is  an  interesting 
point  that  in  many  cases  of  vomiting  due  to  brain  lesions 


128  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

there  is  no  preliminary  nausea.  This  observation  agrees  with 
the  others  in  suggesting  that  the  sensation  of  nausea  is 
produced  in  the  bowel  and  not  in  the  brain.  If  this  reasoning  is 
valid,  it  can  be  used  as  an  argument  in  favor  of  the  view  that 
some  emetics  tend  to  reverse  the  gradient  in  the  bowel 
because,  in  small  doses,  they  produce  nausea  without  vomiting. 
It  would  be  an  interesting  experiment  to  see  whether  people 
whose  vagi  have  been  cut  across,  as  in  complete  gastric 
resection,  can  experience  nausea  after  taking  emetics,  or 
during  spontaneous  vomiting. 

Some  people  experience  nausea  when  constipated  and  are 
relieved  immediately  after  emptying  the  rectum.  Others  are 
nauseated  after  taking  enemas,  particularly  if  those  enemas 
contain  irritant  substances.  A  few  people  feel  nauseated  also 
when  they  are  hungry,  and  get  relief  immediately  after 
taking  food.  That  probably  restores  the  downward  gradient. 

(6)  COATED  TONGUE  AND  FOUL  BREATH.  It  is  commonly 
supposed  that  the  tongue  in  some  sympathetic  way  reflects 
the  condition  of  the  gastric  mucous  membrane.  I  can  find, 
however,  no  proof  of  any  kind  for  this  view.  It  seems  to  be 
based  on  the  idea  that  many  gastro-intestinal  upsets  are 
due  to,  or  associated  with  a  gastritis.  The  recent  more  careful 
study  of  stomachs  which  have  been  filled  with  formalin 
solution  immediately  after  death,  and  the  work  done  on 
sections  removed  at  operations  have  shown  that  gastritis  is 
a  rather  rare  disease  (Beitzke45).  About  the  only  place  in 
which  it  is  found  is  in  the  neighborhood  of  large  gastric 
ulcers,  carcinomatous  and  benign.  It  would  seem  now  to  be 
a  poor  diagnosis  to  make  even  in  alcoholics.  Hirsch,190  has 
shown  that  true  inflammatory  changes  are  hard  to  demon- 
strate even  in  the  stomachs  of  patients  dying  from  delirium 
tremens. 


REVERSE  PERISTALSIS  129 

By  far  the  best  explanation  for  the  coated  tongue  has  been 
given  by  Kast.224  He  gave  lycopodium  powder  in  sealed 
capsules  to  a  number  of  persons,  and  was  able  to  recover  the 
typical  spores  in  the  mouths  of  most  of  them  the  next 
morning.  I  have  had  no  difficulty  in  confirming  these  experi- 
ments. In  one  case,  that  of  a  woman  who  regurgitates  a  good 
deal,  particularly  during  the  menstrual  period,  the  tongue 
became  yellow  from  the  lycopodium. 

It  is  possible  that  some  of  the  particles  making  up  the 
coat  of  the  tongue  may  come  from  even  below  the  stomach. 
Griitzner172  and  also,173  and  others  (Swiezynski,418  Reach,371 
Hemmeter,184  Bernheim,50)  have  shown  in  animals  and  in 
men  that  lycopodium  spores,  or  other  finely  divided  and 
easily  recognizable  material  given  in  enemas  will  travel  in  a 
few  hours  from  the  rectum  to  the  stomach.  Similarly, 
Uffenheimer,436  Dieterlen127  and  others  found  that  bacillus 
prodigiosus  injected  into  the  rectum  could  be  recovered  from 
the  pharynx  a  few  hours  afterwards,  when  every  precaution 
had  been  taken  to  prevent  the  animals  from  licking  them- 
selves or  from  touching  their  feces.  Transmission  through  the 
blood  stream  was  pretty  well  ruled  out.  In  cases  of  pelvic 
peritonitis  with  intestinal  obstruction,  I  have  seen  a  brown 
coating  on  the  tongue  with  a  typical  fecal  odor  long  before 
fecal  vomiting  appeared.  Hence  it  seems  to  me  most  probable 
that  many  of  the  coated  tongues  which  we  see  are  due  to  the 
regurgitation  of  gastric  and  intestinal  contents,  especially 
during  the  night.  This  view  is  strengthened  by  the  fact  that 
the  coating  is  often  heaviest  at  those  times  when  belching, 
regurgitation  and  the  feeling  of  "biliousness"  are  most 
pronounced. 

Laymen  and  physicians  often  feel  that  the  bad  breath, 
coated  tongue  and  bad  taste  in  the  mouth  with  constipation 
are  due  to  the  exhalation  of  absorbed  toxins  which  have 


130  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

come  through  the  blood.  I  have  given  elsewhere  my  reasons 
for  putting  little  faith  in  these  theories  of  auto-intoxication 
(Alvarez19).  The  bad  breaths  of  people  with  diabetes  and 
nephritis,  or  of  people  who  are  dying  may  be  due  to  exhaled 
substances,  but  I  think  the  mechanism  is  quite  different  in 
constipation.  There  it  seems  more  probable  that  the  odor 
comes  from  actual  intestinal  material  deposited  on  the  back 
of  the  tongue.  I  need  hardly  say  that  the  reverse  currents 
must  not  be  blamed  for  every  coated  tongue.  There  are  other 
factors  often  present  in  the  nose,  mouth,  pharynx  and 
salivary  glands  which  must  be  studied  in  individual  cases. 

(7)  FEELING  OF  FULLNESS  AFTER  BEGINNING  TO  EAT.  In 
rare  cases  this  may  be  due  to  an  actual  shrinkage  in  the 
capacity  of  the  stomach  following  ulceration  of  various  kinds, 
but  ordinarily  the  roentgen  ray  examination  will  show  a 
normal  or  even  a  dilated  stomach  (Leven  and  Barrett,261 
p.  142;  personal  observations).  Sometimes  the  patient 
ascribes  his  feeling  of  fullness  to  the  presence  of  gas,  but 
again,  a  careful  examination  often  shows  that  he  is  mistaken. 
Carlson96  (p.  in)  has  shown  moreover,  that  these  sen- 
sations do  not  arise  in  the  gastric  mucous  membrane. 
Hurst201  pp.  22  and  28)  found  that  they  may  arise  if  the 
intestine  is  distended  too  rapidly  by  food  coming  through 
a  gastro-enterostomy  opening;  and  I  have  seen  the  same 
thing  during  jejunal  feeding.  It  seems  to  me  very  suggestive 
that  these  sensations  are  often  associated  with  other  signs 
of  back  pressure.  Sometimes  this  pressure  is  so  strong  that 
the  patient  Can  hardly  swallow.  He  says  that  the  food  does 
not  seem  to  want  to  go  down,  or  that  he  feels  as  if  something 
met  it  and  pushed  it  back.  That  apparently  is  one  of  nature's 
methods  of  telling  us  that  the  gradient  is  reversed  and  that 
the  tract  is  not  prepared  to  receive  food.  The  intensity  of 


REVERSE  PERISTALSIS  131 

this  feeling  in  some  instances  is  well  shown  in  a  case  described 
in  Chapter  XI. 

(8)  GLOBUS.     A  few  times  in  my  life  I  have  happened  to 
swallow  while  a  wave  of  regurgitation  was  on  its  way  up  the 
esophagus,  and  when  the  two  waves  met  there  was  a  painful 
tearing  feeling.   It  may  be  that  globus  is  brought  about 
somewhat  in  that  way   (Marshall  Hall177).  Some  patients 
describe  it  as  a  lump  moving  up  and  down  the  esophagus, 
and  it  is  suggestive  that  the  hysterical,  who  are  supposed  to 
suffer  most  from  globus,  sometimes  present  the  most  striking 
manifestations  of  reverse  peristalsis. 

(9)  HICCUP.     There  is  no  doubt  that  under  certain  con- 
ditions of  diaphragmatic  irritability,  involuntary  belchings 
of  gas  or  waves  of  esophageal  regurgitation  will  be  followed 
immediately  by  a  spasmodic  contraction  of  hiccup.  Similar 
contractions  will  sometimes  be  excited  by  swallowing.  In 
these  cases  it  seems  likely  that  the  diaphragm  is  stimulated 
either  by  a  sudden  distension  of  the  fibers  around  the  eso- 
phageal opening  or  else  by  the  action  current  of  the  eso- 
phageal muscle.  The  latter  theory  seems  not  improbable 
because  the  diaphragm  has  been  observed  to  twitch  rhy- 
thmically under  the  stimulus  of  the  action  current  of  the 
heart.   It  is  suggestive  that  hiccup  is  not  infrequently  a 
troublesome  symptom   after  serious  operations   when  the 
gastro-intestinal  currents  are  plainly  reversed.  Other  factors 
are  undoubtedly  at  work,  and  there  probably  are  many 
varieties  of  hiccup  in  which  reverse  peristalsis  plays  no  part. 

(10)  "BILIOUSNESS."     This  is  often  nothing  more  than 
the   layman's   term   for  the   reverse   peristalsis   syndrome. 
Certainly,   few  thinking  physicians  to-day   would   ascribe 


132  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

that  group  of  symptoms  to  hepatic  insufficiency,  although 
they  are  often  seen  with  definite  gallbladder  disease.  More 
often  the  reverse  waves  seem  to  be  due  purely  to  the  stag- 
nation of  the  colonic  contents  in  constipation.  Biliousness 
derives  its  name  probably  from  the  fact  that  the  sufferers 
note  bile  in  the  regurgitated  or  vomited  material.  As  the 
presence  of  bile  in  the  stomach  is  normal,  any  excess  need 
not  indicate  disease  of  the  liver  so  much  as  an  increase  in 
the  normal  duodenal  regurgitation.  Many  of  these  people 
are  found  at  operation  to  have  actual  organic  disease  like 
cholecystitis  or  chronic  appendicitis;  others,  whose  attacks 
are  ushered  in  by  violent  headaches  have,  I  believe,  a  heredi- 
tary brain  disease;  a  sort  of  sensory  epilepsy.  Some  irritable 
area  in  the  brain  seems  to  send  a  "storm"  down  the  vagus 
which  upsets  the  intestinal  gradient  much  as  it  is  upset  in 
seasickness  or  Meniere's  disease.  In  a  number  of  cases  I  have 
seen  the  severity  of  the  symptoms  and  perhaps  the  number 
of  attacks  diminished  after  the  removal  of  a  diseased  gall- 
bladder or  appendix,  but  a  little  fatigue  could  still  bring  on  a 
typical  headache. 

The  relief  which  these  people  derive  from  purgation,  and 
particularly  purgation  by  calomel  is  due  not  to  any  action 
on  the  liver  (for  all  pharmacologists  are  agreed  that 
there  is  no  cholagogue  action),  but,  I  believe,  to  a  restora- 
tion of  the  downward  current.  The  relief  comes  so  promptly 
after  the  evacuation  of  the  bowel  that  I  am  sure  it  cannot 
be  due  to  the  removal  of  a  source  of  toxins  (Alvarez,19 
p.  12).  If  the  symptoms  were  due  to  circulating  poisons 
they  would  have  to  wear  off  gradually  like  those  of  an 
alcoholic  debauch. 

Those  who  may  feel  that  I  have  appropriated  too  many 
of  the  gastro-intestinal  symptoms  for  this  syndrome  should 
remember  what  I  said  at  the  beginning  of  this  chapter. 


REVERSE  PERISTALSIS  133 

If,  as  seems  likely,  symptoms  are  produced  almost  entirely 
by  disturbances  in  motor  functions,  we  should  be  most 
conscious  of,  and  most  annoyed  by,  the  severest  possible 
form  of  such  disturbance,  namely,  a  reversal  of  the  current. 
In  other  words,  many  or  most  of  the  sensations  which 
reach  our  sensoriums  when  digestion  is  disturbed,  should  be 
those  originating  in  reverse  peristalsis. 


CHAPTER  XI 
OBJECTIONS  AND  DIFFICULTIES 

AS  I  stated  in  the  Introduction,  the  first  question  that 
bothers  many  clinicians  is:  What  relation  have  my 
ideas  on  peristalsis  to  the  current  theories  about 
vagotonia  and  sympathicotonia?  Many  men  are  satisfied 
that  these  two  magic  words  explain  everything;  but  their 
views  are  often  so  hazy  that  they  cannot  be  sure  whether 
my  findings  require  new  mental  adjustments  on  their  part 
or  not.  Similarly,  one  finds  the  author  of  a  recent  textbook 
quoting  in  one  breath  the  "beautiful  work  of  Gaskell  and 
Eppinger  and  Hess,"  apparently  quite  oblivious  to  the  fact 
that  the  one  spent  most  of  his  life  gathering  exact  data 
which  knock  the  supports  out  from  under  the  theorizing  of 
the  other  two.  It  seemed  well,  therefore,  to  review  briefly  the 
function  of  the  extrinsic  nerves  of  the  digestive  tract. 
After  having  to  emphasize  so  strongly  the  autonomy  of  the 
tract  and  the  importance  of  local  muscular  mechanisms,  it  is 
well  to  point  out  that  there  are  extrinsic  nerves  and  that  they 
have  functions.  Before  saying  what  these  functions  are  I 
must  say  what  they  are  not. 

THE  EXTRINSIC  NERVES  OF  THE  DIGESTIVE  TRACT.  The 
usual  statement  found  in  textbooks  is  that  the  autonomic 
(vagi  and  sacral  nerves)  stimulate,  and  the  sympathetic 
fibers  inhibit  the  intestine.  Disease  is  supposed  to  follow  an 
unbalance  between  these  two  effects.  This  unbalance  can 
be  diagnosed  and  corrected  by  the  use  of  certain  drugs  which 

134 


OBJECTIONS  AND  DIFFICULTIES  135 

are  supposed  to  be  elective  in  their  actions.  These  theories  of 
vagotonia  and  sympathicotonia  have  had  a  strange  fasci- 
nation for  the  medical  mind;  they  have  been  dragged  in 
with  the  utmost  assurance  to  explain  all  sorts  of  disease 
states,  and  I  believe  have  had  a  most  unfortunate  influence 
on  our  conceptions  of  gastro-intestinal  physiology.  It  may 
be  that  these  theories  will  eventually  prove  useful,  but  in 
my  opinion  their  foundations  are  so  shaky  that  some  day 
the  whole  edifice  is  going  to  go.  In  the  following  brief  dis- 
cussion I  can  only  point  out  a  few  places  in  which  the  propo- 
nents of  these  theories  have  made  things  much  simpler  than 
they  really  are. 

Although  in  the  main,  the  vagus  tends  to  stimulate  and 
the  sympathetic  to  inhibit  the  stomach  and  bowel,  these 
effects  are  generally  transient;  often  indecisive,  and  not 
infrequently  reversed  (Cannon,86  p.  198;  May,302  Kelling,234 
Weil443).  They  vary  with  the  strength  of  the  stimulus  and 
with  the  condition  of  the  muscle.  The  first  effect  of  vagus 
stimulation  is  generally  a  lowering  of  the  tone.  After  from 
fifteen  to  sixty  seconds  there  may  be  an  increase  of  tone 
and  activity  which  lasts  a  few  seconds  or  minutes  and  then 
disappears.  Spadolini406  (also407)  has  shown  recently  that  one 
can  get  purely  inhibitory  effects  by  stimulating  the  vagus, 
and  purely  augmentor  effects  by  stimulating  the  splanchnics. 
Opposite  effects  can  be  obtained  in  different  parts  of  the 
gut  from  one  and  the  same  stimulus.  Weak  currents  tend  to 
inhibit  while  strong  ones  stimulate.  According  to  Bercovitz 
and  Rogers,48  a  tetanizing  current  stimulates  and  an  inter- 
rupted one  inhibits.  Bunch77  found  that  splanchnic  stimu- 
lation inhibits  in  the  cat  but  generally  augments  the 
movements  in  the  dog. 

Another  difficulty  with  the  vagotonic  theories  is  that 
the  vagus  is  not  a  simple  nerve  like  the  motor  roots  supplying 


136  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

the  voluntary  muscles  of  a  frog.  It  is  a  plexus:  a  bundle  of 
nerves  of  all  sorts  and  sizes,  medullated  and  non-medullated 
(Chase,109  Barratt,36  Edgeworth132).  Most  of  the  fibers 
probably  are  connector  neurones  running  from  the  brain  to 
motor  ganglia  in  Auerbach's  plexus;  but  there  are  also 
afferent  or  sensory  neurones,  and  even  some  sympathetic 
fibers  (Miller,320  Neumann341).  Similarly,  a  "sympathetic" 
nerve  in  the  abdomen  may  consist  of  pre-  and  post-ganglionic 
fibers,  fibers  to  muscles,  fibers  to  blood  vessels  and  glands, 
and  even  sensory  fibers  belonging  to  the  central  nervous 
system.  We  generally  lose  sight  of  the  fact,  too,  that  the 
effect  of  a  strong — often  a  traumatizing  or  damaging — 
electric  shock  is  not  necessarily  the  same  as,  or  even  compar- 
able with  the  effects  produced  by  the  normal,  more  or  less 
continuous  stimuli  which  come  from  the  brain  or  from  the 
sensory  side  of  the  reflex  arcs.  For  this  reason  I  think  we  have 
much  to  learn  yet  about  the  functions  of  the  visceral  nerves. 
One  of  the  strongest  objections  to  the  recent  theories  in 
regard  to  the  autonomic  and  sympathetic  systems  is  that 
they  make  it  appear  that  the  sympathetic  nerves  with  the 
celiac  ganglia  constitute  a  separate  and  distinct  brain  system 
which  can  be  antagonistic  to,  or  out  of  harmony  with  the 
central  nervous  system.  This  view  is  entirely  at  variance 
with  the  facts  which  have  been  collected  and  discussed  in  a 
masterly  way  by  Gaskell  in  his  monograph  on  "The  Involun- 
tary Nervous  System."160  He  shows  that  the  involuntary 
nerves  and  ganglia  are  a  part  of  the  central  nervous  system ; 
that  they  are  connected  with  it  just  as  the  voluntary  nerves 
are,  and  that  they  have  developed  from  the  same  embryonic 
cells  (Abel1).  The  main  difference  is  simply  that  the  motor 
ganglia  which  in  the  voluntary  system  are  found  in  the 
anterior  horns  of  the  cord,  have  migrated;  some  as  far  as 
the  paravertebral  ganglionic  chain;  some  into  the  solar 


OBJECTIONS  AND  DIFFICULTIES  137 

plexus,  and  some  into  the  nerve  nets  in  the  walls  of  the  hollow 
organs.  Hence  it  is  that  the  rami  communicantes  or  pre- 
ganglionic  fibers  in  the  sympathetic  system,  and  most  of 
the  efferent  fibers  in  the  vagus  are  simply  elongated  con- 
nector neurones  such  as  we  find  between  the  motor  and 
sensory  roots  in  the  cord,  and  in  the  pyramidal  tracts. 
Furthermore,  it  has  been  shown  that  there  are  no  com- 
missural  fibers  between  the  different  sets  of  sympathetic 
ganglia  such  as  would  have  to  be  present  if  these  ganglia 
were  to  mediate  reflexes  like  an  abdominal  brain  (Johnson,217 
Langley,248  Carpenter  and  Conel102).  Actually  we  find  that 
the  movements  in  the  involuntary  muscles  connected  with 
these  ganglia  "are  essentially  movements  en  masse,  and 
not  delicately  coordinated  movements,  such  as  are  so 
characteristic  of  the  voluntary  system."  We  see,  then, 
that  the  involuntary  system  is  simply  a  part  of  the  voluntary 
system  characterized  by  the  outward  migration  of  the  motor 
ganglia  and  the  necessary  lengthening  of  the  connector 
neurones.  On  the  sensory  side  there  is  no  difference  between 
the  afferent  fibers  in  a  sympathetic  nerve  and  those  in  a 
spinal  nerve — they  both  go  to  the  posterior  root  ganglion 
in  the  cord  (Langley,249  p.  17). 

We  learn,  then,  from  Gaskell  the  same  lesson  that  we  have 
had  from  Loeb  and  from  Parker:  that  the  nerves  are  there 
to  conduct,  and  not  to  exercise  faculties  requiring  almost 
human  intelligence.  There  are  times  when  the  animal  as 
a  whole  needs  to  communicate  with  its  digestive  tract; 
there  are  times  also  when  the  tract  must  communicate 
with  the  body.  There  are  many  times  when  one  end  of  the  tract 
must  communicate  with  the  other;  and  on  all  these  occasions 
the  extrinsic  nerves  come  into  play.  The  vagi  carry  feelings  of 
hunger  and  of  satiety  from  the  stomach  to  the  brain  (Cohn115) ; 
they  help  in  adjusting  the  tone  of  the  stomach  wall  to  the 


138  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

food  coming  down  the  esophagus  (Cannon,86  p.  200) ; 
and  they  carrry  the  stimuli  that  give  rise  to  the  psychic 
secretion  of  gastric  juice.  If  the  food  must  be  rejected  by 
vomiting,  they  carry  the  impulses  which  bring  the  abdominal 
muscles  to  the  aid  of  the  stomach.  Moreover,  they  probably 
carry  messages  from  the  digestive  tract  which  make  the 
animal  feel  comfortable  and  sleepy  (Loeb,270  p.  96).  The 
splanchnics  serve  largely  to  quiet  the  tract  and  to  stop 
digestion  when  the  body  is  distressed  or  injured  (Cannon,85 
p.  480).  The  extrinsic  nerves  probably  have  much  to  do  with 
the  digestive  upsets  with  disease  elsewhere  in  the  body,  but 
we  saw  in  Chapter  IX  that  these  changes  can  be  accounted 
for  also  by  actual  damage  to  the  gastro-intestinal  muscle. 

The  Law  oj  the  Intestine.  Many  have  asked:  What 
relation  has  the  gradient  idea  to  the  studies  of  Bayliss  and 
Starling,  and  Cannon?  Do  they  conflict,  or  does  the  gradient 
idea  supersede  the  others?  I  think  it  will  be  plain  to  any  one 
who  is  conversant  with  the  literature  on  the  motor  functions 
of  the  digestive  tract  that  there  is  no  serious  conflict. 
Careful  experimental  work  remains  of  value  no  matter 
what  comes  afterwards;  but  as  I  have  said  before,  the  inter- 
pretation based  upon  that  work  oftent  changes  in  the  light 
of  additional  knowledge.  About  the  only  place  in  which 
I  differ  from  Bayliss  and  Starling  and  Cannon  is  in  the 
estimate  put  upon  the  value  of  the  "Law  of  the  Intestine" 
or  the  "Myenteric  Reflex." 

According  to  that  law  (Bayliss  and  Starling,39  p.  no), 
"excitation  at  any  point  of  the  gut  excites  contraction 
above  and  inhibition  below,"  and  that  "reflex"  is  supposed 
to  explain  easily  the  downward  progress  of  food.  There  are 
so  many  objections  to  such  a  view  that  it  is  surprising 
that  no  one  besides  Cannon90  (p.  125)  has  called  attention 
to  them  in  the  last  twenty  years.  In  the  first  place,  the  few 


OBJECTIONS  AND  DIFFICULTIES  139 

who  have  written  about  the  myenteric  reflex  all  admit 
that  it  is  hard  to  demonstrate;  that  it  is  often  absent  and 
often  reversed.  Bayliss  and  Starling  point  out  that  the 
reaction  generally  takes  place  within  a  few  centimeters  of  the 
stimulated  place.  The  inhibition  below  is  confined  mainly 
to  the  circular  muscle  and  it  is  often  absent.  "In  many  cases, 
however,  our  results  have  not  been  quite  so  clear.  Although 
stimulation  above  the  balloon  produced  inhibition,  stimu- 
lation below  produced  also  inhibition  or  preliminary  inhibi- 
tion followed  by  contraction."  Again:  "The  two  effects  do 
,not  run  absolutely  parallel  to  one  another,  in  that  in  some 
experiments  the  inhibitory  effects  from  above,  in  others  the 
augmentor  effects  from  below,  may  be  better  marked." 
These  troubles  persisted  even  after  the  extirpation  of  the 
abdominal  ganglia.  In  another  paper  they  admit  that 
when  they  changed  from  dogs  to  cats  they  did  not  get  good 
pinch  reactions  (according  to  the  law)  until  they  remembered 
that  they  had  always  given  the  dogs  a  preliminary  dose  of 
castor  oil.  Even  when  they  gave  this  drug  to  the  cats  they 
did  not  get  as  typical  reactions  as  they  got  in  the  dog. 
They  had  difficulties  again  when  they  tried  to  use  rabbits  for 
this  work.  It  seems  to  me  that  so  important  a  law  should  be 
capable  of  demonstration  in  all  of  the  laboratory  animals 
without  the  help  of  drugs.  Moreover,  Bayliss  and  Starling 
admit  that  their  technic  could  be  objected  to  because  the 
bowel  is  not  normal  when  it  has  been  opened  so  that  a 
balloon  and  its  attached  rubber  tubing  can  be  put  in.  My 
own  experiments  with  balloons  greatly  impressed  me  with 
the  abnormal  nature  of  the  conditions,  and  made  me  feel 
that  I  could  put  little  trust  in  the  results  obtained. 

Magnus289  (p.  132)  says  he  was  able  to  show  the  law 
on  excised  strips  of  intestine  stimulated  with  a  salt  crystal. 
He  admits,  however,  that  he  could  not  obtain  the  expected 


140  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

reactions  "with  mathematical  regularity. "  In  some  animals  he 
got  inhibition  above  and  below.  Langley  and  Magnus250 
(p.  46)  also  had  considerable  difficulty  in  trying  to  show  the 
law.  They  say:  "It  must  be  noticed  that  although  inhibition 
below  a  point  stimulated  was  so  frequently  obtained,  it  was  in 
any  one  experiment,  which  lasted  two  to  three  hours,  very 
inconstant;  at  one  time  the  inhibition  would  be  marked  and 
at  another  absent,  and  the  period  during  which  one  or  the 
other  state  supervened  was  sometimes  at  the  beginning  of  an 
experiment,  sometimes  an  hour  or  two  later."  Degenerative 
section  of  the  greatest  majority  of  the  superior  mesenteric 
nerves  did  not  abolish  the  reactions,  showing  that  their 
mechanism  is  located  in  the  bowel  wall. 

Cannon  realized  fully  that  the  "myenteric  reflex,"  as  he 
called  it,  is  not  always  demonstrable.  "What  causes  (it)  to 
appear  or  not  when  material  is  present,  is  as  yet  undeter- 
mined ...  It  does  not  govern  the  rhythmic  contractions 
of  the  small  intestine,  the  rhythmic  peristalsis  and  anti- 
peristalsis  of  the  colon,  and  probably  not  the  rhythmic  waves 
of  the  stomach."  (Cannon,90  p.  125;  and  also,86  p.  195.) 

Miss  Starkweather  and  I  studied  the  graphic  records  of  the 
contractions  resulting  from  over  two-thousand  stimuli 
(mechanical,  electrical  and  chemical)  applied  to  the  intestine 
(mainly  of  rabbits)  and  found  that  the  usual  response  in  all 
but  about  twenty  of  the  experiments  was  a  contraction 
above  and  below  (Fig.  21).  Most  of  the  few  responses  that 
corresponded  to  the  law  were  obtained  by  distending  the 
bowel  with  a  small  balloon.  One  objection  to  our  experiments 
is  that  in  most  of  them  the  records  were  taken  from  the 
longitudinal  muscle,  while  Bayliss  and  Starling  got  their 
results  mainly  with  the  circular.  Another  objection  that  can 
be  made  to  all  the  work  done  so  far  is  that  the  stimuli  used 
are  abnormal.  What  we  want  to  know  is  how  the  bowel 


OBJECTIONS  AND  DIFFICULTIES  141 

behaves  above  and  below  a  loop-ful  of  the  usual  intestinal 
contents.  My  own  records  taken  with  a  number  of  entero- 
graphs  show  no  sign  of  any  descending  inhibition  in  front  of 
small  peristaltic  rushes  (Fig.  3).  On  the  other  hand,  the 
bowel  ahead  of  such  waves  often  contracts  powerfully  so  as 
to  keep  them  from  going  too  far.  If  it  were  not  for  that 


FIG.  21. — A  coil  of  jejunum  8  cm.  long  in  an  intact  rabbit  (abdomen  opened 
under  salt  solution)  was  made  to  record  at  both  ends.  When  this  bowel  was 
stimulated  faradically  near  the  upper  recording  thread  it  responded  below; 
when  it  was  stimulated  near  the  lower  end,  it  did  not  respond  above.  When 
stimulated  midway  between,  the  twitch  at  the  lower  end  was  greater.  Note 
the  absence  of  the  myenteric  reflex. 

mechanism  our  digestive  tracts  would  promptly  be  emptied 
of  everything  in  them. 

It  seems  clear  from  the  foregoing  that  the  law  of  the 
intestine  needs  further  study  and  it  needs  restatement. 
Perhaps  it  is  more  strictly  a  response  of  the  circular  muscle 
to  distension;  and  it  may  be  that  we  can  say  later  why  it 
can  be  elicited  one  moment  and  not  the  next,  or  in  one 


142  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

animal  and  not  another.  There  is  much  anatomical  evidence 
to  show  that  it  is  not  a  "reflex;"  that  is,  the  necessary 
nervous  arc  can  not  be  demonstrated  in  the  intestinal  wall. 
Gaskell160  has  pointed  out  that,  at  most,  it  may  be  what  is 
called  an  axon  reflex.  Another  argument  against  the  "reflex" 
is  that  it  has  not  been  helpful  to  the  clinician  in  explaining 
the  peculiarities  of  peristalsis,  particularly  in  disease.  It 
seems  to  me  that  if  it  were  really  fundamental  it  should  be 
exceedingly  helpful  in  practice,  much  as  the  gradient  theory 
is  helpful. 

I  believe  that  the  great  tendency  to  contraction  at  the 
upper  end  of  a  bolus  may  perhaps  be  explained  on  the  basis 
of  the  gradient.  I  showed  in  a  previous  chapter  that  smooth 
muscle,  especially  when  in  connection  with  a  nerve  net, 
responds  first  at  the  point  where  the  tension  or  pressure  is 
greatest  (von  Uexkiill435).  Now,  if  the  tone  of  the  muscle 
in  a  tube  is  everywhere  the  same — if  there  is  no  gradient— 
and  if  the  bolus  is  perfectly  cylindrical,  the  distending  force 
will  be  equal  along  that  bolus  and  the  tendency  to  contract- 
ion will  be  the  same  everywhere.  There  are  two  ways  in 
which  the  contractions  might  be  thrown  to  one  end  or  the 
other.  The  bolus  might  be  somewhat  conical,  in  which  case 
the  muscle  would  be  more  stretched  at  the  end  with  the 
greater  diameter;  or  the  primary  tension  or  tone  of  the 
muscle  might  be  graded,  in  which  case  a  purely  cylindrical 
bolus  would  stimulate  more  at  the  more  tonic  end  of  the 
loop.  As  I  have  considerable  evidence  to  show  that  the  tone 
of  the  muscle  is  actually  graded  from  the  duodenum  to  the 
ileum  (see  Chapter  VII),  we  can  easily  explain  the  fact  that 
the  muscle  contracts  most  actively  on  the  orad  side  of  a  bolus. 

KEITH'S  THEORY.  Another  question  which  some  have 
asked  is :  What  is  the  relation  of  the  gradient  theory  to  the 


OBJECTIONS  AND  DIFFICULTIES  143 

zone  theory  of  Keith?  In  two  articles  published  in  1915, 
Dr.  Keith  reported  the  finding  of  certain  cells  associated 
with  Auerbach's  plexus,  cells  which  he  thought  were  inter- 
mediate between  muscle  and  nerve,  and  which  were  very 
similar  to  those  in  the  Keith- Flack  node  of  the  heart.  Shortly 
after  making  this  discovery  he  read  my  first  two  communi- 
cations on  intestinal  rhythm,  and  was  much  impressed  by 
the  fact  that  the  terminal  segment  of  the  ileum  sometimes 
sets  the  pace  for  a  short  stretch  of  bowel  immediately  above. 
He  argued  from  that  that  the  little  collections  of  "nodal 
tissue"  which  he  had  found  at  the  cardia  and  ileocecal 
sphincter,  and  other  collections  which  he  did  not  find,  but 
which  he  thought  might  be  present  in  the  duodenum,  upper 
jejunum  and  middle  small  intestine,  are  centers  dominating 
the  rhythm  and  activity  of  those  sections  of  the  tract.  He 
suggested  that  the  "food  is  propelled  through  a  series  of 
zones  or  segments,  each  furnished  with  its  own  pacemaker 
and  its  own  rhythmical  contractions. "  Intestinal  stasis, 
of  the  Arbuthnot  Lane  type,  may  be  due  to  blocks  "at  the 
points  where  one  rhythmical  zone  or  area  passes  into  the 
succeeding  zone."  Since  then,  several  writers  have  been 
much  impressed  with  this  idea.  Unfortunately,  they  seem 
to  have  read  Dr.  Keith's  articles  only  in  abstract,  because 
their  published  diagrams  show  nodal  tissue  at  the  points 
where  Keith  says  he  expected  to  find  it  but  did  not.  More- 
over, they  do  not  seem  to  realize  that  Keith  has  made  no 
physiological  studies  at  all,  but  has  simply  made  some 
suggestions  on  the  basis  of  his  anatomical  findings. 

The  plausible  feature  about  this  theory  is  that  we  know 
that  in  the  heart  the  region  with  the  fastest  rate  sets  the 
pace  for  the  others.  Although  to  the  naked  eye  the  heart 
seems  to  contract  simultaneously  all  over,  graphic  records 
show  that  a  wave  of  excitation  travels  from  the  sinus  to  the 


144  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

ventricles.  Somewhat  similarly,  in  the  stomach,  the  area 
with  the  most  rapid  rate  at  the  cardia  appears  to  set  the 
pace  and  we  can  see  the  waves  traveling  slowly  to  the 
pylorus.  In  the  small  intestine,  however,  each  segment 
contracts  at  its  own  rate,  and  only  occasionally  do  we  see 
what  are  called  peristaltic  rushes  running  some  distance 
down  the  bowel.  Although  the  duodenal  muscle  has  the 
fastest  rate  it  does  not  set  the  pace  for  the  rest  of  the  gut. 
I  must  emphasize  this  point  because  several  writers  in  over- 
looking it,  have  theorized  unwarrantedly  on  the  basis  of 
Keith's  findings.  Furthermore,  Miss  Starkweather  and  I18 
have  made  a  careful  study  of  the  regions  suspected  by  Keith 
of  being  pacemakers;  we  have  counted  the  rates  of  rhythmic 
contraction  in  these  segments  and  in  adjoining  ones  before 
and  after  cutting  them  apart,  and  we  have  found  no  sign  of 
any  zones  or  of  any  rhythmic  domination  of  one  segment  over 
another.  Whether  the  ileocecal  ring  has  much  to  do  with  the 
colonic  activities  or  not  I  cannot  as  yet  say.  We  see,  then, 
that  although  it  is  often  most  helpful  to  make  comparisons 
between  the  activities  of  the  heart  tube  and  the  intestine, 
they  must  be  made  with  great  care  and  with  due  regard  for 
all  the  facts  in  the  case. 

Another  objection  to  arise  in  the  minds  of  many  is:  If 
reverse  peristalsis  is  so  common,  why  do  we  not  see  more  of  it 
with  the  roentgen  ray?  It  seems  to  me  that  there  are  several 
answers  to  this  question.  In  the  first  place,  it  must  be 
remembered  that  we  generally  screen  patients  during 
intervals  when  they  are  not  acutely  ill  and  are  not  showing 
many  symptoms.  If  we  could  watch  the  movements  of  the 
bowel  in  the  acute  stages  of  appendicitis,  in  acute  ileus,  or 
during  the  first  two  or  three  days  after  intra-abdominal 
operations,  we  should  probably  see  enough  reverse  peristalsis. 
Actually  we  do  see,  not  infrequently,  reverse  waves  in  the 


OBJECTIONS  AND  DIFFICULTIES  145 

stomach  and  duodenum.  Very  rarely  I  have  seen  them  in 
the  terminal  ileum.  Unfortunately,  the  food  goes  so  rapidly 
through  the  jejunum  and  upper  ileum  that  we  can  seldom 
see  what  is  going  on  there. 

It  must  be  remembered  also  that  many  of  the  disturbances 
seem  to  be  due  to  ripples  which  are  not  deep  enough  to  force 
the  barium  along  the  bowel.  As  I  have  shown  in  Chapter  IX, 
there  is  no  doubt  that  a  small  peristaltic  rush  in  the  lower 
ileum,  or  a  wave  that  forces  material  through  the  ileocecal 
sphincter  is  often  part  of  a  ripple  that  has  come  from  the 
duodenum.  One  might  not  suspect  it  if  it  were  not  shown  so 
clearly  on  the  records  obtained  with  six  or  seven  entero- 
graphs,  recording  simultaneously.  These  ripples  do  not 
move  material  in  the  bowel  unless  they  break  into  peristaltic 
rushes  or  into  defecating  movements  in  the  colon.  They  are 
like  waves  of  the  ocean  which  do  not  carry  a  boat  with  them 
for  any  distance  unless  they  are  breaking  on  a  shelving 
beach.  Similarly,  in  the  digestive  tract,  ripples  in  the  orad 
direction  breaking  into  waves  at  the  cardia  may  cause  many 
of  the  symptoms  of  indigestion. 

Another  point  to  be  remembered  is  that  animal  experi- 
ments suggest  that  the  gradient  may  be  more  nearly  flat- 
tened or  reversed  in  one  segment  of  the  tract  than  another, 
so  that  there  may  be  reverse  waves  in  the  stomach  and 
normal  ones  in  the  intestine.  That  would  tend  to  complicate 
the  problem.  To  my  mind,  the  best  answer  to  be  made 
to  those  who  cannot  accept  the  idea  of  reverse  peristalsis  until 
they  see  more  of  it  with  the  roentgen  ray  is  that  if  they  wait 
for  that,  they  will  fail  to  recognize  what  is  going  on  in  the 
milder,  more  common  disturbances.  Similarly,  if  they  wait  to 
diagnose  gall-bladder  disease  until  the  patient  has  colic, 
jaundice  and  demonstrable  stones,  they  will  miss  perhaps 
95  per  cent  of  the  early  cases.  It  seems  reasonable  to  suppose 
10 


146  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

that  the  brain  of  a  sensitive  man  or  child  should  detect,  or 
in  some  way  become  conscious  of,  abnormalities  in  peristalsis 
long  before  they  are  severe  enough  to  become  visible  on  the 
roentgen  ray  screen.  Furthermore,  these  disturbances  are 
often  so  transient  that  it  would  be  hard  to  demonstrate 
them  objectively. 

To  illustrate:  two  healthy  boys,  seven  and  eight  years  of 
age,  respectively,  ate  heartily  of  blackberries  at  dinner. 
The  next  morning  the  younger  one  had  diarrhea,  but  the 
elder  seemed  all  right.  Early  in  the  afternoon,  however,  he 
began  to  complain  of  dizziness,  a  queer  feeling  of  pressure 
in  his  pharynx,  and  recurrent  waves  of  nausea  which  came 
every  twenty  or  thirty  minutes.  Once  or  twice  he  retched 
unsuccessfully.  Between  the  attacks  of  nausea  he  played 
happily.  At  supper  time  he  made  several  attempts  to  eat, 
but  each  time  said  the  food  would  not  go  down;  something 
seemed  to  push  it  back.  He  then  felt  like  defecating  and  with 
the  help  of  an  enema  passed  a  hard  plug  of  feces.  Shortly 
afterwards  he  had  a  large  soft  movement  containing  the 
remains  of  the  blackberries,  and  immediately  after  that  he 
asked  for  food.  He  then  found  he  could  eat  a  large  meal 
without  any  difficulty.  This  child  appears  then  to  have  had 
a  series  of  reverse  waves  which  arose  in  a  colon  distended 
by  irritant  material.  These  waves  were  perceived  by  him  as 
surges  of  nausea  and  dizziness,  as  a  tension  in  the  throat, 
and  an  inability  to  swallow.  The  upset  in  the  gradient  was 
such  that  the  tract  would  not  accept  food.  Although  these 
sensations  were  very  definite  so  far  as  the  child  was  con- 
cerned, it  might  have  been  impossible  to  show  much  change 
with  the  roentgen  ray  beyond,  perhaps,  a  gastric  stasis; 
and  it  might  have  been  difficult  to  show  much  even  with  a 
series  of  enterographs.  If,  however,  the  lower  bowel  had  not 
been  emptied  when  it  was,  he  probably  would  have  vomited 


OBJECTIONS  AND  DIFFICULTIES  147 

large  amounts  of  intestinal  fluid  next  day,  and  a  few  days 
later  the  fluid  might  have  been  fecal  in  character.  There 
would  then  have  been  no  doubt  about  the  existence  of 
reverse  peristalsis. 

This  case  brings  up  still  another  point,  and  that  is  that 
we  can  probably  study  reversals  of  peristalsis  more  satis- 
factorily in  children  than  in  adults.  The  intestine  in  children 
is  short,  its  various  parts  are  functionally  knit  together,  it  is 
very  sensitive,  and  its  gradient  is  easily  reversed.  Hence  it 
is,  perhaps,  that  organic  lesions  often  produce  just  those 
symptoms  which  would  be  expected  according  to  the  gradient 
theory.  In  adults,  various  complicating  factors  may  enter  to 
obscure  the  picture. 

Another  question  is:  How  can  signs  of  reverse  peristalsis 
appear  from  time  to  time  during  digestion,  when  food  is 
actually  going  down  the  tract?  This  objection  does  not  seem 
insuperable  when  we  remember  that  waves  can  travel  at  the 
same  time  in  different  directions  over  one  medium.  Recently 
I  stood  on  the  banks  of  a  stream  which  was  flowing  north. 
The  wind  was  blowing  hard  enough  to  make  wavelets 
traveling  in  the  opposite  direction.  A  passing  launch  pro- 
duced other  waves  which  came  from  the  east  and  were 
reflected  at  the  shore.  Three  types  of  waves  could  easily 
be  identified  going  in  three  directions  over  water  which  was 
flowing  in  a  fourth.  It  may  be  that  ripples  can  travel  up  and 
down  the  intestine  in  much  the  same  way.  They  may, 
perhaps,  skip  regions  in  which  the  gradient  is  fairly  normal 
to  produce  anastalsis  in  regions  where  it  is  reversed.  It 
must  be  remembered  also 'that  liquids  can  be  forced  through 
portions  of  the  tract  in  which  the  gradient  is  definitely 
reversed.  This  is  shown  by  the  experiments  in  which  sections 
of  bowel  are  cut,  reversed,  and  anastomosed  again.  We 
know  also  that  fluid  introduced  into  the  colon  under  pressure 


148  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

can  be  made  to  run  out  at  the  mouth.  Moreover,  liquids 
will  go  through  stretches  of  bowel  in  which  the  muscle  is 
paralyzed  or  from  which  it  has  actually  been  removed 
(KreidI  and  MuIIer,242  MuIIer  and  Kondo335).  We  need 
not  think  always  of  the  food  as  going  with  the  gradient  and 
the  ripples  against  it,  because  in  parts  of  the  tract  the 
ripples  might  conceivably  be  going  with  the  gradient  and  the 
food  against  it.  It  must  be  remembered,  of  course,  that  this 
discussion  is  at  present  quite  theoretical.  There  is  some 
analogy,  perhaps,  in  the  heart,  where  the  blood  may  continue 
to  travel  in  the  usual  direction,  although  the  electrocardio- 
graph shows  that  the  ventricle  is  contracting  a  fraction  of  a 
second  ahead  of  the  auricle. 

The  difficulties  which  have  bothered  me  most  have  been 
connected  with  the  lack  of  absolute  parallelism  between  the 
various  gradients  under  certain  conditions  and  in  some  parts 
of  the  tract.  For  instance,  although  asphyxia  and  KCN  are 
supposed  to  affect  the  metabolic  gradient  in  the  same  way, 
and  although  the  tracings  shown  in  figures  1 7  and  1 8  are 
remarkably  alike  so  far  as  amplitude  of  contraction  is  con- 
cerned, they  are  not  alike  as  regards  rhythmicity.  KCN 
markedly  slows  the  rate  of  contraction  and  asphyxia  affects 
it  little  or  not  at  all  until  it  is  stopped  entirely.  Moreover, 
asphyxia  has  little  effect  on  the  colon,  while  KCN  depresses 
its  activities.  Theoretically,  KCN  should  have  less  effect 
on  the  colon  than  on  the  ileum  if  the  severity  of  the  reaction 
is  dependent  solely  upon  the  oxygen  need  of  the  tissue. 

There  are  a  number  of  such  technical  problems  which 
await  solution  during  the  coming  years,  and  the  answers  to 
them  will  undoubtedly  modify  some  of  my  present  views. 
Fortunately,  however,  the  best  discoveries  often  come 
through  the  solution  of  difficulties  which  at  first  seem  most 
embarrassing  and  most  disturbing. 


CHAPTER  XII 
TECHNICAL  METHODS  AND  APPARATUS 

A  much  of  the  technic  for  the  experiments  described  in 
this  little  book  had  to  be  worked  out  as  I  went  along, 
and  as  many  details  which  I  learned  from  Dr.  Cannon 
and  others  are  not  to  be  found  in  textbooks,  it  occurred  to 
me  that  a  short  chapter  on  apparatus  and  methods  might 
be  gratefully  received,  particularly  by  beginners  in  this  field 
of  research. 

As  Cannon  and  Auer  have  pointed  out,  the  early  physiolo- 
gists were  greatly  hampered  in  their  study  of  the  intestinal 
movements  by  the  fact  that  the  opening  of  the  abdomen  has 
a  strong  inhibiting  effect.  For  this  reason  most  of  their 
conclusions  were  based  on  observation  of  the  powerful 
writhing  movements  which  appear  just  after  the  death  of 
an  animal.  The  early  studies  have  little  value  also  because 
the  bowel  was  allowed  to  dry  in  the  air;  and  we  know  that 
that  has  a  disturbing  effect.  In  1871,  Sanders  and  Van 
Braam  Houckgeest  made  a  big  improvement  by  opening 
the  animals  under  a  bath  of  salt  solution.  That  prevented 
the  drying,  but  conditions  were  still  not  entirely  normal. 
Much  work  was  done  with  fistulae  into  various  parts  of  the 
tract  and  with  balloons  passed  through  the  mouth,  but  here 
again  many  objections  can  be  raised. 

THE  ROENTGEN  RAY  AND  THE  BARIUM  MEAL.  It  was 
not  until  1896,  when  Professor  Bowditch  suggested  to 
Cannon,  then  a  student,  that  he  use  the  newly  discovered 
roentgen  ray,  that  we  were  supplied  with  an  entirely  trust- 

149 


i5o  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

worthy  method  for  studying  the  movements  of  the  ali- 
mentary canal  (Bowditch71  ).  Incidentally,  it  should  be  noted 
that  it  is  this  method  which  is  now  being  used  so  universally 
and  so  satisfactorily  in  medical  practice  on  man.  As  this 
technic  for  animals  is  well  described  on  pages  5  to  7  of 
Cannon's  book,86  I  shall  not  go  into  details  here.  Barium 
sulfate  "for  x-ray  use"  is  now  used  instead  of  the  bismuth 
subnitrate  which  occasionally  becomes  toxic  in  the  bowel. 
The  best  animals  to  use  are  tame  old  female  cats  which  will 
not  object  to  handling,  because  any  anger  or  excitement 
stops  the  intestinal  movements.  The  most  satisfactory 
apparatus  would  consist  now  of  a  small  transformer  and  a 
self-rectifying  Coolidge  tube.  If  the  laboratory  budget  is, 
low,  the  student  may  be  able  to  buy  very  cheaply  an  old 
roentgen  ray  coil  with  a  mercury  jet  interrupter.  Although 
these  outfits  are  very  satisfactory  for  radioscopy,  dealers 
in  roentgen  ray  apparatus  generally  have  a  roomful  of 
them  which  they  can  not  sell  any  more.  Great  care  should 
be  taken  to  see  that  the  operator  is  protected  from  all  stray 
radiations  and  from  contact  with  the  high  tension  wires. 
The  room  must  be  absolutely  dark  and  after  entering  it  the 
student  should  not  attempt  to  work  for  half  an  hour  or  more 
until  his  retina  is  fully  adjusted.  The  roentgen  ray  method  is 
now  little  used,  probably  because  there  is  little  hope  of 
seeing  anything  new  which  Cannon  or  the  many  clinical 
roentgenologists  have  not  already  described.  I  think, 
however,  that  it  should  be  used  more  and  more  by  the 
pharmacologists. 

METHOD  OF  AUER.  Auer24  made  a  number  of  interesting 
observations  on  rabbits  whose  abdomens  were  shaved.  He 
found  he  could  watch  the  movements  of  the  cecum  quite 
satisfactorily  through  the  thin  abdominal  wall.  Very  simi- 


TECHNICAL  METHODS  AND  APPARATUS        151 

larly,  I  have  been  able  to  study  rhythmic  segmentation  in 
people  with  large  hernias,  where  the  bowel  lay  under  a  thin 
coat  of  peritoneum  and  skin. 

GASTRIC  AND  DUODENAL  TUBES.  For  this  technic  the 
reader  is  referred  particularly  to  the  articles  by  Carlson,96 
and  his  associates.  They  have  done  a  lot  of  excellent  physio- 
logic work  on  the  movements  of  the  human  stomach,  using 
these  tubes  and  balloons.  Most  of  this  work  was  concerned 
with  the  hunger  contractions  and  with  secretion.  Wheelon 
and  Thomas  444  point  out  that  a  balloon  which  can  slip  around 
in  the  stomach  is  not  likely  to  give  an  entirely  satisfactory 
record  of  what  is  going  on  there,  so  they  anchor  a  special 
type  of  metal  tambour  in  the  antrum  and  in  the  pyloric 
canal.  McCIendon306  (p.  180)  has  studied  the  hydrogen  ion 
concentration  of  the  gastric  and  intestinal  juices  by  letting 
down  a  specially  designed  electrode  on  the  end  of  a  wire. 

FISTULAE.  First  should  be  mentioned  the  Heidenhain- 
Pavloff  stomach  which  is  so  designed  that  the  experimenter 
can  study  gastric  secretion  under  many  conditions.  A  flap 
of  stomach  wall  is  dissected  up  and  formed  into  a  pouch 
which  empties  externally  through  a  fistula.  This  technic 
will  be  found  described  in  the  first  chapter  of  PavIofPs 
book  on  "The  Work  of  the  Digestiye  Glands,355  and  in 
excellent  articles  in  the  Ergebnisse  der  Physiologic3™  (1902), 
and  in  Tigerstedt's  "Handbuch  der  physiologi.sche  Me- 
thodik."356  In  order  to  obtain  pure  gastric  juice,  Pavloff 
performed  the  operation  of  esophagotomy  on  dogs  already 
possessing  gastric  fistulae;  that  is,  he  divided  the  esophagus 
in  the  neck  and  allowed  the  upper  end  to  heal  into  the  skin 
incision.  When  such  dogs  are  given  food  it  drops  out  of  the 
esophageal  opening,  but  the  psychic  stimulus  causes  a  flow 
of  gastric  juice. 


152  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

Thiry  studied  the  intestinal  juices  by  closing  off  one  end 
of  a  loop  of  bowel  and  sewing  the  other  to  an  opening  in  the 
abdominal  wall.  Vella437  brought  both  ends  into  the  skin 
incision  so  as  to  be  able  to  study  the  progress  of  balls  and 
bits  of  food  through  the  loop.  Others  have  made  fistulae  into 
various  parts  of  the  intestine  in  order  to  study  the  pyloric 
function  and  the  succus  entericus  (Cohnheim  and  Dreyfus,117 
Best  and  Cohnheim,52;53  Baumstark,37  London,272 Thomsen,425 
Baumstark  and  Cohnheim,38  von  Mering,318  Hirsch189). 
Especially  when  making  duodenal  fistulae  it  is  helpful 
to  have  the  stoma  as  near  as  possible  to  the  spine  of 
the  animal  so  that  gravity  will  favor  and  not  hinder  the 
keeping  of  the  animal  clean.  Another  method  is  to  sew  the 
unopened  bowel  to  the  skin  and  then  to  introduce  or  remove 
material  with  a  large  hypodermic  syringe,  the  needle  of 
which  is  thrust  through  the  wall. 

WINDOWS.  Van  Braam  Houckgeest194  tried  to  use  glass 
windows  in  the  abdominal  wall,  and  others  (Sabbatani,381 
Katsch,226  Katsch  and  Borchers,227  and  Zondek456)  have 
since  done  considerable  work  with  animals  which  have  been 
operated  upon  in  this  way.  Watch  glasses  or  pieces  of 
celluloid  are  generally  used,  and  with  care  the  animals 
can  be  kept  alive  and  well  for  some  time.  They  are  useful 
for  pharmacologic  studies  or  for  class  demonstrations. 

OPENING  UNDER  SALT  SOLUTION.  For  the  careful  analysis 
of  the  intestinal  movements  it  seems  to  me  that  we  shall 
have  to  turn  more  and  more  to  the  method  which  was 
devised  and  first  used  by  Sanders.382  As  his  papers  were 
published  in  a  small  Dutch  journal  they  dropped  into 
oblivion,  and  the  technic  is  generally  ascribed  to  Van  Braam 
Houckgeest.194  Sanders'  article  shows  considerable  ability; 


TECHNICAL  METHODS  AND  APPARATUS        153 

and  it  is  interesting  that  he  was  the  first  to  describe  reverse 
peristalsis  in  the  colon.  Houckgeest's  article  is  also  well 
worth  reading  to-day.  Only  with  the  animal  opened  can  one 
get  the  kymographic  records  which  are  so  essential  for  the 
exact  analysis  of  muscular  movements  and  conduction; 
and  only  in  this  way  can  one  orient  himself  properly  so  as 
to  know  what  part  of  the  bowel  is  being  studied;  which 
end  orad,  etc.  The  animal  can  be  anesthetized  most  con- 
veniently with  urethan,  2  grams  per  kilo,  by  mouth.  A 
catheter  can  be  passed  into  the  esophagus  through  a  hole 
in  a  small  spindleshaped  gag.  Every  care  should  be  taken 
to  see  that  this  catheter  gets  into  the  stomach  and  not  into 
the  trachea.  If  the  animal  should  show  any  signs  of  returning 
sensation,  more  urethan  should  be  injected  through  a  fine 
needle  into  the  duodenum.  After  the  animal  is  thoroughly 
anesthetized  a  canula  may  be  put  into  the  trachea,  although 
this  is  not  always  necessary.  In  order  to  avoid  much  of  the 
inhibition  which  comes  from  opening  the  abdomen,  the 
spinal  cord  should  generally  be  destroyed  from  a  point  just 
above  the  sacrum  to  the  interscapular  region.  A  small 
incision  is  made  over  the  lower  lumbar  spine;  an  opening  is 
made  between  two  laminae  and  a  large  copper  wire  is  thrust 
up  through  the  canal  as  far  as  the  interscapular  region. 
The  wound  is  then  closed  with  a  suture.  The  greatest  care 
should  be  taken  while  opening  the  abdomen  to  cut  exactly 
in  the  median  line.  Only  in  this  way  can  one  avoid  hemor- 
rhage which  is  hard  to  stop  in  the  bath,  and  which  can  soon 
obscure  the  field  of  vision.  The  animal  should  be  washed  and 
then  put  into  the  bath.  I  use  a  copper  tank,  8  inches  wide, 
9^  inches  deep,  and  31  inches  long,  with  an  electric  heater 
and  thermo-regulator.  It  has  a  row  of  metal  eyelets  along 
the  bottom,  to  which  the  animal's  paws  may  be  attached,  if 
necessary.  Jacobj212  used  a  vertical  tank  which  he  thought 


154  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

had  certain  advantages.  It  had  a  glass  window  on  one  side 
through  which  the  bowel  could  be  observed.  The  bath  should 
consist  either  of  0.8%  sodium  chloride  solution  or  else 
Locke's  solution  of  the  following  composition. 

NaCI 9 .  oo 

KCI 42 

CaCI2  anhydrous .24 

NaHCO3 20 

H2O 1000 . oo 

I  now  use  the  Locke's  solution,  although  I  do  not  know 
whether  the  results  are  any  more  satisfactory  than  those 
with  plain  salt  solution.  If  good  movements  are  to  be  obtain- 
ed, the  animal  should  be  fed  shortly  before  anesthetization. 
Some  men  give  aloin  or  castor  oil  the  night  before,  but 
Taylor  and  I  (Alvarez  and  Taylor23)  have  shown  that 
purgation  alters  the  gradients  and  damages  the  muscle  in 
places.  Every  care  should  be  taken  to  get  normal  and  frisky 
animals.  As  defecation  into  the  tank  is  often  annoying  when 
working  with  cats,  the  rectum  can  be  tied  off  with  a  piece  of 
tape.  The  animal's  head  can  be  held  in  proper  position  by  an 
ordinary  Tschermak  head-holder  which  is  fastened  to  the 
edge  of  the  tank. 

The  movements  can  be  observed  visually  or  they  can  be 
recorded  mechanically  by  means  of  balloons  or  some  form 
of  enterograph.  The  use  of  balloons  is  unsatisfactory  for 
several  reasons.  They  are  foreign  bodies;  they  block  the 
lumen  of  the  gut;  they  cause  bleeding;  and  the  trauma 
incident  to  their  introduction  often  overshadows  any 
other  stimuli  that  one  may  be  trying  to  record.  Of  all  the 
methods  for  recording  intestinal  contractions  mentioned  in 
Tigerstedt's  "Handbuch  der  physiologische  Methodik,"296 
the  one  that  comes  nearest  to  the  requirements  for  good  work 


TECHNICAL  METHODS  AND  APPARATUS        155 

is  the  enterograph  of  Bayliss  and  Starling.  This,  however,  is 
rather  too  elaborate;  it  is  not  easily  fastened  to  the  bowel 
wall,  and  it  must  be  kept  above  the  level  of  the  salt  solution. 
Figure  22  shows  on  the  left,  a  type  of  enterograph  which  I 
designed  several  years  ago  and  which  has  enabled  me  to  get 
satisfactory  records  from  several  parts  of  the  bowel  at  one 


FIG.  22. — On  the  left  is  shown  the  simple  type  of  recorder  ordinarily  used. 
On  the  right  is  a  similar  one,  made  of  silver  with  a  small  tambour  instead  of 
the  rubber  teat. 

time.  This  simple  and  cheap  little  apparatus  consists  of  two 
pieces  of  sheet  aluminum,  two  short  lengths  of  piano  wire 
and  a  small  rubber  teat.  I  first  used  the  teat  which  is  made 
for  springing  the  shutters  in  large  commercial  cameras. 
When  the  supply  of  these  (from  England)  was  cut  off  by  the 
war,  I  used  the  triangular  little  bags  which  are  supplied 
for  the  ends  of  stirring  rods.  The  rubber  teat  should  be 


156  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

cemented  to  the  aluminum  only  on  one  side.  When  fastened 
on  both  sides  it  is  likely  to  bind  and  the  apparatus  is  less 
sensitive.  The  other  arm  of  the  little  lever  is  fastened  to  the 
peritoneal  coat  of  the  bowel  by  means  of  a  little  wire  serre- 
fine.  This  generally  has  to  be  made  by  the  student  himself 
if  it  is  to  grip  firmly  and  not  spring  open  all  the  time.  A 
series  of  these  recorders  can  be  fastened  to  a  number  of 
tambours  which  write  one  above  the  other  on  a  smoked  sur- 
face. For  a  while,  during  the  war,  when  I  could  not  get  any 
form  of  rubber  teat  I  fastened  a  small  tambour  to  one  side 
of  the  enterograph  as  shown  in  the  figure,  but  I  found  this 
less  sensitive  than  the  much  cheaper  and  simpler  form.  The 
little  serrefines  are  much  more  convenient  than  any  form  of 
hook  or  sewed-on  apparatus  because  the  tone  of  the  bowel 
changes  rapidly  from  time  to  time  and  the  observer  must  be 
able  to  take  up  slack  quickly  and  without  undue  handling. 
The  only  place  where  the  recorders  do  not  work  well  is  on 
the  colon.  That  contracts  down  so  hard  at  times  that  it  tears 
away  from  the  instruments,  leaving  them  hanging  to  shreds 
of  peritoneum.  When  one  wishes  to  record  the  intestinal 
movements  in  only  one  or  two  places  it  is  best  to  follow  the 
technic  which  I  have  described  elsewhere  (Alvarez  and 
Starkweather18).  One  end  of  a  loop  is  held  down  by  a  serre- 
fine  fastened  on  the  end  of  a  rod,  and  the  other  end  pulls 
on  a  heart  lever  which  writes  on  a  drum  which  can  be  placed 
over  the  tank  immediately  above  the  animal. 

Slowtzoff402  and  Trendelenburg430  have  described  methods 
for  recording  the  contractions  of  a  loop  of  bowel  through 
holes  made  through  the  abdominal  wall  of  an  anesthetized 
animal  but  I  can  see  no  advantages  over  the  tank  method 
if  one  has  a  tank  handy.  Courtade  and  Guyon120  used  loops 
of  bowel  removed  from  the  abdomen  but  still  attached  by  a 
section  of  mesentery.  Hofmeister  and  Schiitz191  did  a  lot  of 


TECHNICAL  METHODS  AND  APPARATUS        157 

work  with  the  excised  stomach  in  a  moist  chamber.  I  have 
found  it  convenient  to  run  steam  from  a  flask  of  boiling 
water  into  the  chamber.  It  not  only  keeps  the  tissue  moist, 
but  it  keeps  it  warm.  Sick  and  Tedesco400  studied  the  excised 
stomach  in  oxygenated  Locke's  solution.  Carnot"  and 
Glenard168  perfused  the  intestine  excised  from  the  body  as  a 
whole. 

SMALL  EXCISED  SEGMENTS.  Haffter176  seems  to  have  been 
the  first  to  learn  that  excised  segments  of  intestine  will 
continue  to  contract  rhythmically.  Magnus289  deserves  most 
credit  for  having  worked  out  the  details  of  the  method  which 
•often  goes  by  his  name.  I  have  modified  it  to  the  extent  that 
I  use  several  segments  at  a  time  in  the  same  bath.  The 
animal  is  killed  with  chloroform  or  with  a  blow  on  the  head. 
It  is  then  opened,  and  pieces  from  25  to  50  cm.  in  length 
are  removed  from  various  parts  of  the  bowel  and  strung  on  a 
safety  pin  in  proper  order,  and  with  the  orad  end  towards 
the  pin.  These  segments  can  be  kept  then  in  iced  Locke's 
solution  and  smaller  pieces  cut  off  as  needed  during  the  day. 

1  generally  use  at  least  five  segments  at  one  time,  suspended 
between  serrefmes  in  a  beaker  containing  about  400  c.c.  of 
Locke's  solution.  This  is  kept  in  a  water  bath  at  38°  C.  It  is 
oxygenated   by   a  small  stream   of  compressed   air  which 
bubbles  through  it.  When  four  or  five  segments  are  used 
at  one  time  they  should  be  cut  fairly  short;  that  is,  about 

2  cm.  long,  and  special  levers  should  be  used.  The  Harvard 
Apparatus  Company  (Back  Bay  postoffice,  Boston)  made 
me  some,  30  cm.  long,  with  an  adjustable  pivot  so  that  the 
ratio  between  the  arms  can  be  varied  at  will.  If  the  ordinary 
heart  levers  are  used,  the  magnification  is  so  great  that  all 
the  records  will  not  go  on  a  drum  of  the  standard  size.  If  a 
large  amount  of  Locke's  solution  is  used,  the  segments  con- 


158  THE  MECHANICS  OF  THE  DIGESTIVE  TRACT 

tract  more  regularly  and  for  a  longer  period  of  time,  probably 
because  their  metabolites  are  well  diluted.  It  is  only  when 
using  rare  drugs  or  small  amounts  of  vital  fluids  that  one 
needs  to  use  a  smaller  amount  of  solution.  As  I  have  pointed 
out  before  (Alvarez,2)  when  making  pharmacologic  studies 
with  such  small  amounts,  one  must  be  careful  to  see  that  the 
temperature  remains  constant  within  tenths  of  a  degree; 
otherwise  erroneous  conclusions  may  easily  be  drawn. 
Whenever  possible,  the  pharmacologist  should  use  several 
segments  at  one  time  to  serve  as  checks,  one  on  another. 
Anyone  who  will  look  over  some  of  the  figures  in  my  six- 
teenth article  (Alvarez16)  will,  I  think,  be  impressed  with 
the  need  for  that  precaution. 

When  studying  conduction,  the  myenteric  reflex  and  other 
phenomena,  the  technique  described  in  my  eighteenth  article 
(Alvarez  and  Starkweather18)  is  very  useful.  There  I  show 
how  records  can  be  obtained  from  both  ends  of  a 
segment  by  turning  them  up  like  a  U. 

Sometimes  it  is  desired  to  compare  the  contractions  of 
the  circular  and  longitudinal  muscles,  or  to  study  the  action 
of  drugs  on  the  inner  surface  of  the  bowel.  For  such  work 
the  student  may  use  the  technic  described  by  Gayda162 
and  Morishima  and  Fujitani.326 

For  the  latent  period  work  I  have  used  a  simple  moist 
chamber  made  out  of  a  wide-mouthed  six-ounce  bottle.  The 
lower  end  of  the  segment  is  fastened  by  a  serre-fine  to  a 
metal  "L"  support  which  is  thrust  through  the  rubber 
stopper.  The  other  end  of  the  segment  is  fastened  to  the 
metal  heart  lever  by  means  of  a  fine  copper  wire.  The 
current  can  be  led  to  the  segment  through  these  two 
metal  connectons.  The  apparatus  for  the  metabolic  work  and 
the  catalase  experiments  will  be  found  described  in  articles 
by  Miss  Starkweather  and  me.11 


TECHNICAL  METHODS  AND  APPARATUS        159 

The  student  who  plans  to  do  research  work  in  gastro- 
enterology  or  the  physician  who  wishes  to  know  more  about 
the  mechanical  factors  of  digestion  should  study  carefully 
Cannon's  classic  book  on  the  subject.  Bayliss  and  Starling's 
three  articles,  and  one  by  Elliott  and  Barclay-Smith  should 
also  be  read  and  re-read.  Magnus'  articles  in  the  Ergebnisse,295 
and  in  Tigerstedt's  "Handbuch,"296  are  also  very  helpful.  Much 
good  physiology  will  be  found  in  excellent  books  and  articles 
by  Carman,98  Barclay,33  Carlson,96  Case,105  and  Hurst.199 

For  information  on  the  chemical  side  of  digestion  the 
student  should  turn  to  the  splendid  books  of  Pavloff,355 
Cohnheim,116  and  Babkin.27  Bab  kin  is  Pavloff's  assistant 
at  Petrograd,  and  his  book  summarizes  the  work  done 
in  Russia  up  to  the  beginning  of  the  War. 

Wingate  Todd's427  splendid  little  book  presents  the  anat- 
omy of  the  digestive  tract  from  the  viewpoint  of  a  man  who 
is  thoroughly  conversant  with  the  work  of  the  physiologist 
and  the  roentgenologist.  Those  who  would  like  to  know  some- 
thing about  the  comparative  anatomy  of  the  tract  should 
turn  to  Oppel,346  Huntington,196  and  Mitchell.322  The 
subject  of  comparative  physiology  has  been  well  covered 
by  Jordan.222 

The  real  student  of  a  subject  must  always  know  something 
about  its  history  and  development.  Access  to  the  older 
literature  can  easily  be  obtained  through  the  little  book  of 
Poensgen;360  and  the  articles  of  Cary,103  Pearce,357  Cannon,91 
and  Crane121  will  be  found  very  interesting.  American 
students  will  be  interested  also  in  the  work  of  Beaumont,42 
the  "Backwoods  Physiologist."  His  book  contains  little 
of  scientific  interest  for  us  today,  but  it  makes  up  for  it 
with  the  wealth  of  inspiration  which  it  can  give  to  any  young 
man  who,  with  little  outside  help  or  recognition,  will  struggle 
onward  with  his  work. 


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1.  ABEL,  W.  Further  observations  on  the  development  of  the  sympathetic 
nervous  system  in  the  chick.  J.  Anat.  &  PbysioL,  1912,  47,  35-72. 

2.  ALVAREZ,  W.  C.   I.   Functional  variations  in  contractions  of  different 
parts  of  the  small  intestine.  Am.  J.  PbysioL,  1914,  35,  177-193. 

3.  ALVAREZ,  W.  C.  II.  Further  studies  on  intestinal  rhythm.  Am.  J.  PbysioL, 
1915,  37,  267-281. 

4.  ALVAREZ,  W.  C.  III.  The  motor  functions  of  the  intestine  from  a  new 
point  of  view.  J.  Am.  M.  Assn.,  1915,  65,  388-394. 

5.  ALVAREZ,  W.  C.  IV.  Differences  in  rhythmicity  and  tone  in  different 
parts  of  the  wall  of  the  stomach.  Am.  J.  PbysioL,  1916,  40,  585-602. 

6.  ALVAREZ,  W.  C.  V.  Differences  in  irritability  and  latent  period  in  different 
parts  of  the  wall  of  the  stomach.  Am.  J.  PbysioL.  1916,  4J,  321-332. 

7.  ALVAREZ,  W.  C.  VI.  Differences  in  latent  period  and  form  of  the  con- 
traction curve  in  muscle  strips  from  different  parts  of  the  frog's  stomach. 
Am.  J.  PbysioL,  1917,  42,  422-434. 

8.  ALVAREZ,  W.  C.  VII.  Differences  in  latent  period  and  form  of  the  contrac- 
tion curve  in  muscle  strips  from  different  parts  of  the  mammalian  stomach. 
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9.  ALVAREZ,  W.  C.  IX.  The  syndrome  of  mild  reverse  peristalsis.  J.  Am. 
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12 


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INDEX  OF  AUTHORS 


1.  Abel,  136  39. 

2.  Alvarez,  26,  37,  8 1,  158 

3.  Alvarez,  25,  26,  37,  53,  72,  121  41. 

5.  Alvarez,  18,  37,  59,  62  42. 

6.  Alvarez,  18,  19,  66  43. 

7.  Alvarez,  18,  68,  81 

8.  Alvarez,  18,  68,  81  44. 

9.  Alvarez,  115  45. 

10.  Alvarez,  10,  18,  23,  37,  79,  81  46. 

1 1 .  Alvarez  and  Starkweather,  39,        47. 

45,  81,  87,  158  48. 

12.  Alvarez,  93  49. 

13.  Alvarez  and  Starkweather,  18  50. 

14.  Alvarez  and  Starkweather,  69,         51. 

81  52. 

16.  Alvarez,  93,  158  53. 

17.  Alvarez  and  Starkweather,  37,         54. 

106  55. 

1 8.  Alvarez  and  Starkweather,  13,         56. 

15,  41,  144,  156,  158  58. 

19.  Alvarez,  130,  132  59. 

23.  Alvarez  and  Taylor,  95,  154  60. 

24.  Auer,  150  61. 

25.  Aufschnaiter,  22,  23  62. 

26.  Austin,  120  63. 

27.  Babkin,  159  64. 

28.  Babkin,  121  65. 

29.  Bancroft  and  Esterly,  35  67. 

30.  Barbera,  66  68. 

31.  Barclay,  127  69. 

32.  Barclay,  29  70. 
33-  Barclay,  159  71. 

34.  Barclay,  104  72. 

35.  Barclay,  104  73. 

36.  Barratt,  136  74. 

37.  Baumstark,  152  75. 

38.  Baumstark  and  Cohnheim,  152         76. 

185 


Bayliss  and  Starling,  10,  39,  54, 

102,  138 

Bayliss  and  Starling,  14 

Beaumont,  159 

von  Bechterew  and  Weinberg, 

117 

Beer  and  Eggers,  39 
Beitzke,  128 
Bellamy,  47 
Bensley,  62 

Bercovitz  and  Rogers,  135 
von  Bergmann,  99 
Bernheim,  129 
Best  and  Cohnheim,  96 
Best  and  Cohnheim,  96,  152 
Best  and  Cohnheim,  152 
Bethe,  4 
Bethe,  2 
Biedermann,  54 
Biedermann,  14 
Biedermann,  41,  53 
Bine  and  SchmoII,  105 
Bokai,  54,  101 
Boldireff,  97,  101 
Boldireff,  115 
Borgbjarg,  104 
Boring,  123 
Bottazzi,  26,  56,  75 
Bottazzi,  56 
Bottazzi,  35 

Bottazzi  and  Griinbaum,  16 
Bowditch,  150 

Brandl  and  Tappeiner,  42,  56 
Brinton,  22 
von  Briicke,  75 
von  Briicke,  26,  40,  53 
Buchanan,  87 


1 86 


INDEX  OF  AUTHORS 


77.  Bunch,  135  1 20. 

78.  Burrows,  12  121. 

79.  Campbell,  119  122. 

80.  Cannon,  29  123. 

81.  Cannon,  4,  15,  70,  73  124. 

82.  Cannon,  99  125. 

83.  Cannon,  98,  101,  121  126. 

84.  Cannon,  32,  53  127. 

85.  Cannon,  138  128. 

86.  Cannon,  14,  18,  19,  27,  29,  33,       129. 

39,  53,  135,  138,  140,  150  130. 

87.  Cannon,  32,  53,  80  131. 

88.  Cannon,  53  132. 

89.  Cannon,  72  133. 

90.  Cannon,  53,  138,  140  134. 

91.  Cannon,  159  135. 

92.  Cannon  and  Blake,  100  136. 

93.  Cannon  and  Murphy,  100  137. 

94.  Carlson,  13,  40  138. 

95.  Carlson,  65  139. 

96.  Carlson,  21,  130,  151,  159  140. 

97.  Carlson  and  Braafladt,  122  141. 

98.  Carman,  159  142. 

99.  Caraot,  157  143. 

102.  Carpenter  and  Conel,  137  144. 

103.  Carey,  159  145. 

104.  Case,  27,  29  146. 

105.  Case,  159  147. 

1 06.  Case,  27,  29,  30,  1 02  148. 

107.  Case,  29 

1 08.  Cash,  24  149. 

109.  Chase,  136  150. 
no.  Child,  78  151. 
in.  Child,  13  152. 

112.  Child,  85  153. 

113.  Child,  45,  47,  48,  49,  51  154. 

114.  Chlumski,  117  155. 

115.  Cohn,  97,  137  156. 

116.  Cohnheim,  159  157. 

117.  Cohnheim    and    Dreyfus,    118,       158. 

127,  152  159. 

118.  Cohnheim  and  Dreyfus,  100  160. 

119.  Cole,  97,  104  161. 


Courtade  and  Guyon,  156 

Crane,  159 

CuIIis  and  Tribe,  84 

Cunningham,  22 

Deaver,  105 

Demarquay,  107 

Dagaew,  96 

Dieterlen,  129 

Dietlen,  27 

Dittler,  72 

Drummond,  106 

Ducceschi,  65 

Edge  worth,  136 

Edmunds,  12 

Egan,  99 

Eggleston  and  Hatcher,  93 

Elliott,  26,  27,  28 

Elliott,  28 

Elliott  and  Barclay  Smith,  119 

Enderlen  and  Hess,  39 

Engelmann,  32,  44 

Engelmann  and  Van  Brakel,  28 

Eppinger  and  Hess,  90 

Esslemont,  26 

Ewald,  103,  115 

Exner,  14 

Eyster  and  Meek,  36,  84 

Farr,  127 

Faulhaber  and  von  Redwitz,  72, 

118 

Faulhaber  and  von  Redwitz,  99 
Fisher,  12 
Fletcher,  12 
Flint,  57 
Floel,  54 

Forbes  and  Gregg,  1 1 
Friedlander,  33 
Fubini,  24 
Garrey,  n 
Gaskell,  34 
Gaskell,  35,  60 
Gaskell,  12,  28,  136,  142 
Gault,  80 


INDEX  OF  AUTHORS 


187 


162.  Gayda,  158  204. 

163.  von  Gehuchten,  100  205. 

164.  Gerlach,  43,  57  206. 

165.  Gilmer,  95  207. 

166.  Ginsburg,   Tumpowsky,    and       208. 

Hamburger,  122  209. 

167.  Glafster  and  Logan,  85  210. 

168.  Glenard,  157  211. 

169.  Greene  and  Gilbert,  87  212. 

170.  Groedel,  71  213. 

171.  Griitzner,  20  214. 

172.  Grutzner,  129  215. 

173.  Grutzner,  129  216. 

174.  Gunn  and  Underbill,  9  217. 

175.  Haane,  62  218. 

176.  Haffter,  157  219. 

177.  Hall,  131  220. 

178.  Halsey,  84  221. 

179.  Hart,  84  222. 

1 80.  Haudek  and  Stigler,  95  223. 

181.  Hecht,  14,  35  224. 

182.  Hedblom  and  Cannon,  104  225. 

183.  Heile,  28  226. 

184.  Hemmeter,  129  227. 

185.  Hermann,  49  228. 

1 86.  Herschell,  120  229. 

187.  Hess,  41,  56  230. 

1 88.  Hippocrates,  122  231. 

189.  Hirsch,  100,  118,  152  232. 

190.  Hirsch,  128  233. 

191.  Hofmeister  and  Schutz,  70,  156        234. 

192.  Holzknecht,  29  235. 

193.  Hooker,  41  236. 

194.  Van  Braam  Houckgeest,  54,  152      237. 

195.  Hunter,  35,  84  238. 

196.  Huntington,  60,  159  239. 

197.  Hurst,  29  240. 

198.  Hurst,  29  241. 

199.  Hurst,  104,  159  242. 

200.  Hurst,  122  243. 

20 1.  Hurst,  123,  130  244. 

202.  Hurst,  95  245. 

203.  Hurst,  26,  104  246. 


Hurst,  96 

Hurst  and  Newton,  29,  29 

Hutchinson,  120 

Hyman,  45 

Hyman,  85 

Hyman,  78 

Hyman,  45 

Ingvar,  50 

Jacob],  29,  57,  153 

Jacob),  14,  1 02 

Jefferson,  62 

Jenkins  and  Carlson,  14,  71 

Jennings,  17 

Johnson,  137 

Jonas,  96 

Jonnesco,  57 

Jordan,  14 

Jordan,  4 

Jordan,  159 

Kastle  and  Bruegel,  24,  29,  106 

Kast,  129 

Kantor,  125 

Katsch,  94,  152 

Katsch  and  Bore  hers,  152 

Katsch  and  Bore  hers,  14 

Keith,  26 

Keith,  143 

Keith,  143 

Keith  and  Jones,  60 

Kelling,  39,  115 

Kelling,  101,  102,  135 

Kienbock,  102 

Kirschner  and  Mangold,  14,  72 

Kirstein,  39,  102 

Knowlton  and  Moore,  1 5 

Kolbing,  117 

KoIIiker,  57 

Krehl,  4,  70 

KreidI  and  MuIIer,  148 

Kretschmer,  32 

Krogh,  58 

Kuntz,  43,  57 

Kuroda,  28 


i88 


INDEX  OF  AUTHORS 


247.  Kussmaul,  100  289. 

248.  Langley,  137  290. 

249.  Langley,  137  291. 

250.  Langley  and  Magnus,  140  292. 

251.  Langmann,  115  293. 

252.  Lansdown  and  Williamson,  62          295. 

253.  Lapique,  16  296. 

254.  Laqueur,  56  297. 

255.  La  tar  jet  and  Forgeot,  58  298. 

256.  Lebon  and  Auburg,  28  299. 

257.  Ledderhose,  117  300. 

258.  Lee,  Guenther  and  Meleney,  47      301. 

259.  Legors  and  Onimus,  56  302. 

260.  Lenk  and  Eisler,  99  303. 

261.  Leven  and  Barrett,  130  304. 

262.  Lewis,  60  305. 

263.  Lewis,  8 1  306. 

264.  Lewis  and  Lewis,  12  309. 

265.  Lewis  and  Mathison,  87  311. 

266.  Lillie,  14,  22,  34,  78 

267.  Lillie,  49,  78  312. 

268.  LJIIie,  22  313. 

269.  Lintwarew,  121  314. 

270.  Loeb,  3,  4,  n,  12,  138  315. 

271.  Loeb,  12 

272.  London,  152  316. 

273.  Long  and  Fenger,  99  317. 

274.  Lowenthal,  122,  123  318. 

275.  Lucas,  36  319. 

276.  Luciani,  56  320. 

277.  Luckhardt,  Phillips  and  Carlson,      321. 

99  322. 

278.  Liideritz,  54  323. 

279.  Liideritz,  54,  56  324. 

280.  Liideritz,  64  325. 

281.  Luiidin,  95,  99  326. 

282.  Lund,  50  327. 

283.  Luschka,  26,  28  328. 

284.  Lyman,  27  329. 

285.  Macewen,  107  330. 

286.  Mackenzie,  102  331. 

287.  Mackenzie,  102.  333. 

288.  MacArthur  and  Jones,  51  334. 


Magnus,  14,  44,  139,  157 
Magnus,  6 
Magnus,  7 
Magnus,  6 
Magnus,  7 
Magnus,  159 
Magnus,  151,  154,  159 
Maleyx,  102 
Mall,  53,  80 
Mall,  39 

Marbaix,  14,  99,  100 
Mat  hews,  49,  50 
May,  66,  80,  135 
Mayer,  A.  G.,  73 
Mayer,  S.,  14,  8 1 
Mayo,  74 
McCIendon,  151 
McCIendon,  99 
McCIure,  Reynolds  and 

Schwartz,  99 
McCIure  and  Derge,  39 
McGiH,  16 

McGuigan  and  Becht,  15 
McGuigan,   Keaton  and  Sloan, 

15 

Meek,  33 
Meltzer,  64 
von  Mering,  152 
Merkel,  57 
Miller,  81,  136 
Mines,  12 
Mitchell,  159 
Monks,  57 
Monks,  57 
Moore,  15 

Morishima  and  Fujitani,  158 
Moritz,  99 
Morse,  99 
Moynihan,  117 
Moynihan,  96 
Miihsam,  39 
Miiller,  A.,  14 
Miiller  and  Hesky,  106,  107 


INDEX  OF  AUTHORS 


335.  MuIIer  and  Kondo,  148                     378. 

336.  MuIIer,  120  379. 

337.  Miiller-Hettlingen,  49                        380. 

339.  Neilson  and  Lipsitz,  101  381. 

340.  Neuburger,  93  382. 

341.  Neumann,  136  383. 

342.  Niwa,  89  384. 

343.  Nothnagel,  56,  102  385. 

344.  Okinczyc,  58  386. 

345.  Openchowski,  115  387. 

346.  Oppel,  60,  159  388. 

347.  Ostwald,  n  389. 

348.  Parker,  3  390. 

349.  Parker,  14  391. 

350.  Parker,  2,  4,  11,  17  392. 

351.  Parnas,  17  393. 

352.  Paterson,  104  394. 

353.  Paukul,  16  395. 

354.  Pavloff,  151  396. 

355.  Pavloff,  151,  159  397. 

356.  Pavloff,  151  398. 

357.  Pearce,  159  399- 

358.  Penfield,  36  400. 

359.  Peyer,  120  401. 

360.  Poensgen,  159  402. 

361.  Pohl,  56  403- 

362.  Pompilian,  16  404. 

363.  Porter,  15  405. 

364.  Pressler,  41  406. 

365.  Prutz  and  EHinger,  39                       407. 

366.  Prutz  and  EHinger,  39                       408. 

367.  Quimby,  115 

368.  Quirot,  102  409. 

369.  Ranvier,  16  410. 

370.  Raasche,  88  41 1- 

371.  Reach,  129  412. 

372.  Rehfuss,  Bergheim  and  Hawk,      413. 

100  414- 

373.  Reichel,  102  415- 

374.  Reichmann,  173  416. 

375.  Roith,  14,  56  417- 

376.  RoIIeston  and  Jex  Blake,  105          418. 

377.  Rosenberg,  117  419- 


Rost,  57,  1 06 

Rubaschow,  4,  70 

Rutherford,  27,  28 

Sabbatani,  152 

Sanders,  29,  152 

Satani,  36 

Schafer,  57 

Schiefferdecker,  16 

Schillbach,  54 

Schilling,  125 

Schloffer,  115 

Schmidt,  122 

Schultz,  1 6,  20 

Schultz,  20,  84 

Schur,  122,  123 

Schiitz,  122 

Schwartz,  30,  106 

Segale,  78 

Senn,  27,  39 

Sherrington,  15 

Sherrington,  17 

Shimodaira,  102 

Sick  and  Tedesko,  157 

Singer  and  Holzknecht,  106 

Slowtzoff,  156 

Smith  and  Lewald,  121 

Smithies,  104 

Sokoloff  and  Luchsinger,  36 

Spadolini,  80,  135 

Spadolini,  80,  135 

Spencer,    Meyer,    Rehfuss   and 

Hawk,  99 
Steele,  122 

Stewart  and  Barber,  74 
Stierlin,  102 
Stiles,  56,  84 
Stockton,  10 1,  1 20,  122 
Straub,  19 
Straub,  35 
Straub,  79 

Surmont  and  Dubus,  14,  96 
Swiezynski,  129 
Symes,  85 


INDEX  OF  AUTHORS 


420.  von  Tabora,  101,  121 

421.  Takahashf,  95 

422.  Tashiro,  51,  89 

423.  Taylor,  114 

424.  Taylor  and  Alvarez,  44,  79 

425.  Thomson,  152 

426.  Tobler,  100 

427.  Todd,  22,  57,  69,  159 

428.  Toldt,  22,  28 

429.  Tourneux  and  Hermann,  57 

430.  Trendelenburg,  156 

431.  Trendelenburg,  53 

433.  Treves,  115 

434.  Treves,  102 

435.  von  UexkuII,  142 

436.  Uffenheimer,  129 

437.  Vella,  152 

438.  Verson,  23,  28 


439.  Verzar,  n 

440.  Waterston,  65 

441.  Parkes  Weber,  115 

442.  Wegele,  Gross  and  Held,  101 

443.  Weil,  135 

444.  Wheelon  and  Thomas,  99,  151 

445.  White,  102,  104 

446.  Wiedemann,  117 

447.  Williams  and  James,  84 

448.  Wilson,  80 

449.  Wislocki  and  O'Connor,  19,  36 

450.  Wolff,  53 

451.  Wood  worth,  17,  44 

452.  Worden  et  al.,  95 

453.  Yanase,  12 

454.  De  Zilwa,  12,  44 

455.  Zimmermann,  122 

456.  Zondek,  152 


INDEX  OF  SUBJECTS 


Adrenalin,  28,  91  • 

Anastalsis,  30 
Anatomic  differences,  57 
Appendicitis,  104,  125,  126 
Auerbach's  plexus,  6,  13,  43 
Autointoxication,  130,  132 
Autonomy  of  the  digestive  tract,  i ,  4, 
70 

Barium  meal,  149 

Belching,  124,  125 

Bile  in  the  stomach,  117,  132 

Biliousness,  131 

Blood  supply  of  bowel,  57 

Books  for  reference,  159 

Carcinoma,  19,  98,  99,  102 
Cardia,  21,  73 
Catalase,  69 
Coated  tongue,  128 
Colonic  peristalsis,  28 
Comparative  anatomy  of  the  stom- 
ach, 6 1 

Conduction,  3,  13,  32,  137 
Constipation,  105,  122 

Depression  at  lower  end  of  the  gradi- 
ent, 107 

Diarrhea,  24,  96,  101,  122 

Diastalsis,  30 

Dietary  suggestions,  no 

Distension,  response  to,  18 

Duodenal  regurgitation,  100 
ulcer,  75,  97 

Duodenum,  23 

Early  observations  on  the  rhythmic 
gradient,  55 


Electric  action  currents,  33,  49 
Embryology  of  the  stomach,  60 
Emetics,  93,  117,  128 
Esophagus,  21,  59,  123 
Evolution  of  the  nervous  system,  2 
Excised  segments,  157 

Fats,  action  on  stomach  and  bowel, 

101,  121 
Fistulae,  151 

Foreign  bodies,  passage  of,  14 
Foul  breath,  128 
Fullness  after  eating,  130 

Gall-bladder  disease,  21,  75,  97,  120, 

125,  132 

Ganglion  cells,  4 
Gastric  canal,  61 
epithelium,  62 
stasis,  98,  103 
ulcer,  73 
Gastritis,  128 
Gastrocolic  reflex,  26,  104 
Gastroenterostomy,  75,  100 
Globus,  131 
Gradient  idea,  practical  applications 

of  the,  76,  146 
of  force,  41 
of  metabolism,  43 
upsets  in  the,  76 
Gradients,  32 

effects  of  asphyxia,  87,  90 
of  drugs,  88,  91,  93,  124 
of  introduction  of  food,  79 
of  KCN,  85 
of  nervous  stimuli,  80 
of  toxins  upon,  81 
factors  altering  the,  78,  94 


191 


192 


INDEX  OF  SUBJECTS 


Heart  gradient,  34 
Heartburn,  122 
Hiccup,  131 

Hirschprung's  disease,  15 
Hour-glass  stomach,  19 

Ileocecal  regurgitation,  27 

sphincter,  26 
Illustrative  simile,  107 
Intestinal  obstruction,  102,  115,  117 
Irritability,  54,  64 
Irritating  lesions,  78,  102 

Jejunal  feeding,  101 

Katastalsis,  30 
Keith's  theory,  142 

Latent  period,  52,  64 
Law  of  the  intestine,  138 
Laxatives,  91,  94,  132,  154 

Metabolic  gradient,  changes  in,  78 

Murphy  drip,  105 

Muscle,  differences  in,  18,  47 

Muscle  of  the  digestive  tract,  opera- 
tive removal  of,  96,  106 

Myenteric  reflex,  138 

Myogenic  nature  of  the  rhythmic  con- 
tractions, 6 


Nausea,  97,  100,  101,  126, 
Nerve  nets,  2,  142 
Nerves,  function  of,  3 


[46 


Pacemaker,  72,  144 
Peristalsis,  gastric,  21 
Peristaltic  rush,  14,  17,  24,  145 
Primitive  digestive  tube,  59,  60 
Psychic    effects,    81,    95,    102,    127, 

138 
Purges,  19 


Pylorospasm,  15,  75 
Pylorus,  66 

blockage  of  waves,  22,  74,  97 

mechanical  control  of,  98 

Reaction  of  intestinal  contents,  99 
Receptive  relaxation  of  colon,  27 
Rectal  feeding,  105 
Regurgitation,  120 
Reversal  of  segments  of  intestine,  38 
Reverse  peristalsis,  26,  29,  106,  114, 

129,  144,  153 
Rhythmic  gradient  in  the  stomach,  63 

processes  in  nature,  1 1 

segmentation,  24 
Roentgen  ray,  149 

Sick  animals,  84,  90 

Smooth  muscle,  16 

Splanchnic  nerves,  section  of,  4,  70 

Starvation,  97,  100 

Steepening  of  the  gradients,  95 

Stimulation  at  lower  end  of  the  gradi- 
ent, 104 

at  upper  end  of  the  gradient,  95 
in  the  middle  of  the  gradient,  101 

Strychnin/ 1 5 

Sympathetic  nervous  system,  136 

Technical  methods,  149 
Tendency  to  beat  rhythmically,  53 
Tone,  52,  64,  142 

Ulcer,  V-shaped  excision  for,  74 
Ureter,  36 

Uterus,  effects  on  digestion,  118,  121, 
124,  125,  127 

Vagotonia,  134 

Vagus,  effects  of  stimulation,  80,  135 

section  of,  4,  15,  70,  97 
Vomiting,  101,  115,  116,  138 


PAUL  B.  HOEBER 

67-69  EAST  59TH  STREET 

NEW  YORK 


I 


BIOLOGY 

LIBRARY 

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UNIVERSITY  OF  CALIFORNIA  LIBRARY 

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